Permissive software license

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A permissive software license, sometimes also called BSD-like or BSD-style license, [1] is a free-software license which instead of copyleft protections, carries only minimal restrictions on how the software can be used, modified, and redistributed, usually including a warranty disclaimer. Examples include the GNU All-permissive License, MIT License, BSD licenses, Apple Public Source License and Apache license. As of 2016, the most popular free-software license is the permissive MIT license. [2] [3]


Public domain & equivalents Permissive license Copyleft (protective license) Noncommercial license Proprietary license Trade secret
DescriptionGrants all rightsGrants use rights, including right to relicense (allows proprietization, license compatibility)Grants use rights, forbids proprietization Grants rights for noncommercial use only. May be combined with copyleft.Traditional use of copyright; no rights need be grantedNo information made public
SoftwarePD, CC0 BSD, MIT, Apache GPL, AGPL JRL, AFPL proprietary software, no public licenseprivate, internal software
Other creative worksPD, CC0 CC-BY CC-BY-SA CC-BY-NC Copyright, no public licenseunpublished


The following is the full text of the simple GNU All-permissive License:

Copyright <YEAR>, <AUTHORS>

Copying and distribution of this file, with or without modification, are permitted in any medium without royalty, provided the copyright notice and this notice are preserved. This file is offered as-is, without any warranty.


The Open Source Initiative defines a permissive software license as a "non-copyleft license that guarantees the freedoms to use, modify and redistribute". [6] GitHub's choosealicense website describes the permissive MIT license as "[letting] people do anything they want with your code as long as they provide attribution back to you and don't hold you liable." [7] California Western School of Law's defined them as follows: "The 'BSD-like' licenses such as the BSD, MIT and Apache licenses are extremely permissive, requiring little more than attributing the original portions of the licensed code to the original developers in your own code and/or documentation." [1]

Comparison to copyleft

Copyleft licenses generally require the reciprocal publication of the source code of any modified versions under the original work's copyleft license. [8] [9] Permissive licenses, in contrast, do not try to guarantee that modified versions of the software will remain free and publicly available, generally requiring only that the original copyright notice be retained. [1] As a result, derivative works, or future versions, of permissively-licensed software can be released as proprietary software. [10]

Defining how liberal a license is, however, is not something easily quantifiable, and often depends on the goals of the final users. If the latter are developers, for some it might be valuable to have the right to modify and exploit source code written by others and possibly incorporate it into proprietary code and make money with it (and therefore these see permissive licenses as offering them a "right"), [11] while for other developers it might be more valuable to know that nobody will ever capitalize what has mostly been their work (and therefore these see copyleft licenses as offering them a "right"). Furthermore, the final users might not be developers at all, and in this case copyleft licenses offer them the everlasting right to access a software as free software, ensuring that it will never become closed source – while permissive licenses offer no rights at all to non-developer final users, and software released with a permissive license could theoretically become from one day to another a closed source malware without the user even knowing it.

Permissive licenses offer more extensive license compatibility than copyleft licenses, which cannot generally be freely combined and mixed, because their reciprocity requirements conflict with each other. [12] [13] [14] [15] [16]

Comparison to public domain

Computer Associates Int'l v. Altai used the term "public domain" to refer to works that have become widely shared and distributed under permission, rather than work that was deliberately put into the public domain. However, permissive licenses are not actually equivalent to releasing a work into the public domain.

Permissive licenses often do stipulate some limited requirements, such as that the original authors must be credited (attribution). If a work is truly in the public domain, this is usually not legally required, but a United States copyright registration requires disclosing material that has been previously published, [17] and attribution may still be considered an ethical requirement in academia.

Advocates of permissive licenses often recommend against attempting to release software to the public domain, on the grounds that this can be legally problematic in some jurisdictions. [18] [19] Public-domain-equivalent licenses are an attempt to solve this problem, providing a fallback permissive license for cases where renunciation of copyright is not legally possible, and sometimes also including a disclaimer of warranties similar to most permissive licenses.

License compatibility

License compatibility between common free and open-source software (FOSS) licenses according to David A. Wheeler (2007): the vector arrows denote a one directional compatibility, therefore better compatibility on the left side ("permissive licenses") than on the right side ("copyleft licenses"). Floss-license-slide-image.svg
License compatibility between common free and open-source software (FOSS) licenses according to David A. Wheeler (2007): the vector arrows denote a one directional compatibility, therefore better compatibility on the left side ("permissive licenses") than on the right side ("copyleft licenses").

In general permissive licenses have good license compatibility with most other software licenses in most situations. [12] [13]

Due to their non-restrictiveness, most permissive software licenses are even compatible with copyleft licenses, which are incompatible with most other licenses. Some older permissive licenses, such as the 4-clause BSD license, the PHP License, and the OpenSSL License, have clauses requiring advertising materials to credit the copyright holder, which made them incompatible with copyleft licenses. Popular modern permissive licenses, however, such as the MIT License, the 3-clause BSD license and the zlib license, don't include advertising clauses and are generally compatible with copyleft licenses.

Some licenses do not allow derived works to add a restriction that says a redistributor cannot add more restrictions. Examples include the CDDL and MsPL. However such restrictions also make the license incompatible with permissive free-software licenses.[ citation needed ]

Reception and adoption

While they have been in use since the mid-1980s, [21] several authors noted an increase in the popularity of permissive licenses during the 2010s. [22] [23] [24] [25]

As of 2015, the MIT License, a permissive license, is the most popular free software license, followed by GPLv2. [2] [3]

Other terms


A "permissive" license is simply a non-copyleft open source license.

Sometimes the word "permissive" is considered too ambiguous, because all free software licenses are "permissive", in the sense that they all allow to modify and redistribute the source code. In most cases the real opposition is between copyleft licenses and non-copyleft ones, thus some authors prefer to use the term "non-copyleft" instead of "permissive". [27] [28] [26]


Berkeley had what we called "copycenter," which is "take it down to the copy center and make as many copies as you want."

Copycenter is a term originally used to explain the modified BSD license, a permissive free-software license. The term was presented by computer scientist and Berkeley Software Distribution (BSD) contributor Marshall Kirk McKusick at a BSD conference in 1999. It is a word play on copyright, copyleft and copy center. [29] [30]

Pushover license

We call them “pushover licenses” because they can't say “no” when one user tries to deny freedom to others.."

Richard Stallman, founder of the GNU operating system [31]

In the Free Software Foundation's guide to license compatibility and relicensing, Richard Stallman defines permissive licenses as "pushover licenses", comparing them to those people who "can't say no", because they are seen as granting a right to "deny freedom to others." [31] The Foundation recommends pushover licenses only for small programs, below 300 lines of code, where "the benefits provided by copyleft are usually too small to justify the inconvenience of making sure a copy of the license always accompanies the software". [32]

Cuck license

Why be mean and bully BSD and MIT licenses calling them "Cuck Licenses"? Quite simply, using them is precisely analogous to being cuckolded. When you really look at it, the similarity is uncanny."

Luke Smith, author of LARBS [33]

In response to those corporations that put pressure on developers to move away from copyleft licenses in favour of permissive ones, some developers have coined the term "cuck license" [34] [ failed verification ] [35] [ unreliable source? ] (precisely in analogy to being cuckolded), [33] [ This quote needs a citation ] as they perceive that corporations want to benefit from collaborative work and privatize profits without giving anything back.

See also

Related Research Articles

<span class="mw-page-title-main">Free software</span> Software licensed to preserve user freedoms

Free software or libre software is computer software distributed under terms that allow users to run the software for any purpose as well as to study, change, and distribute it and any adapted versions. Free software is a matter of liberty, not price; all users are legally free to do what they want with their copies of a free software regardless of how much is paid to obtain the program. Computer programs are deemed "free" if they give end-users ultimate control over the software and, subsequently, over their devices.

The free software movement is a social movement with the goal of obtaining and guaranteeing certain freedoms for software users, namely the freedoms to run, study, modify, and share copies of software. Software which meets these requirements, The Four Essential Freedoms of Free Software, is termed free software.

<span class="mw-page-title-main">GNU Lesser General Public License</span> Free-software license

The GNU Lesser General Public License (LGPL) is a free-software license published by the Free Software Foundation (FSF). The license allows developers and companies to use and integrate a software component released under the LGPL into their own software without being required by the terms of a strong copyleft license to release the source code of their own components. However, any developer who modifies an LGPL-covered component is required to make their modified version available under the same LGPL license. For proprietary software, code under the LGPL is usually used in the form of a shared library, so that there is a clear separation between the proprietary and LGPL components. The LGPL is primarily used for software libraries, although it is also used by some stand-alone applications.

The MIT License is a permissive free software license originating at the Massachusetts Institute of Technology (MIT) in the late 1980s. As a permissive license, it puts only very limited restriction on reuse and has, therefore, high license compatibility.

<span class="mw-page-title-main">Open-source license</span> Software license allowing source code to be used, modified, and shared

Open-source licenses facilitate free and open-source software (FOSS) development. Intellectual property (IP) laws restrict the modification and sharing of creative works. Free and open-source software licenses use these existing legal structures for the inverse purpose of granting freedoms that promote sharing and collaboration. They grant the recipient the rights to use the software, examine the source code, modify it, and distribute the modifications. These licenses target computer software where source code can be necessary to create modifications. They also cover situations where there is no difference between the source code and the executable program distributed to end users. Open-source licenses can cover hardware, infrastructure, drinks, books, and music.

Viral license is an alternative name for copyleft licenses, especially the GPL, that allows derivative works only when permissions are preserved in modified versions of the work. Copyleft licenses include several common open-source and free content licenses, such as the GNU General Public License (GPL) and the Creative Commons Attribution-ShareAlike license.

<span class="mw-page-title-main">Apache License</span> Free software license developed by the ASF

The Apache License is a permissive free software license written by the Apache Software Foundation (ASF). It allows users to use the software for any purpose, to distribute it, to modify it, and to distribute modified versions of the software under the terms of the license, without concern for royalties. The ASF and its projects release their software products under the Apache License. The license is also used by many non-ASF projects.

The Mozilla Public License (MPL) is a free and open-source weak copyleft license for most Mozilla Foundation software such as Firefox and Thunderbird. The MPL license is developed and maintained by Mozilla, which seeks to balance the concerns of both open-source and proprietary developers; it is distinguished from others as a middle ground between the permissive software BSD-style licenses and the General Public License. So under the terms of the MPL, it allows the integration of MPL-licensed code into proprietary codebases, but only on condition those components remain accessible.

The Common Development and Distribution License (CDDL) is a free and open-source software license, produced by Sun Microsystems, based on the Mozilla Public License (MPL). Files licensed under the CDDL can be combined with files licensed under other licenses, whether open source or proprietary. In 2005 the Open Source Initiative approved the license. The Free Software Foundation (FSF) considers it a free software license, but one which is incompatible with the GNU General Public License (GPL).

This comparison only covers software licenses which have a linked Wikipedia article for details and which are approved by at least one of the following expert groups: the Free Software Foundation, the Open Source Initiative, the Debian Project and the Fedora Project. For a list of licenses not specifically intended for software, see List of free-content licences.

<span class="mw-page-title-main">Public-domain software</span> Software in the public domain

Public-domain software is software that has been placed in the public domain, in other words, software for which there is absolutely no ownership such as copyright, trademark, or patent. Software in the public domain can be modified, distributed, or sold even without any attribution by anyone; this is unlike the common case of software under exclusive copyright, where licenses grant limited usage rights.

<span class="mw-page-title-main">Public-domain-equivalent license</span> License that waives all copyright

Public-domain-equivalent license are licenses that grant public-domain-like rights and/or act as waivers. They are used to make copyrighted works usable by anyone without conditions, while avoiding the complexities of attribution or license compatibility that occur with other licenses.

License proliferation is the phenomenon of an abundance of already existing and the continued creation of new software licenses for software and software packages in the FOSS ecosystem. License proliferation affects the whole FOSS ecosystem negatively by the burden of increasingly complex license selection, license interaction, and license compatibility considerations.

License compatibility is a legal framework that allows for pieces of software with different software licenses to be distributed together. The need for such a framework arises because the different licenses can contain contradictory requirements, rendering it impossible to legally combine source code from separately-licensed software in order to create and publish a new program. Proprietary licenses are generally program-specific and incompatible; authors must negotiate to combine code. Copyleft licenses are commonly deliberately incompatible with proprietary licenses, in order to prevent copyleft software from being re-licensed under a proprietary license, turning it into proprietary software. Many copyleft licenses explicitly allow relicensing under some other copyleft licenses. Permissive licenses are compatible with everything, including proprietary licenses; there is thus no guarantee that all derived works will remain under a permissive license.

<span class="mw-page-title-main">Free-software license</span> License allowing software modification and redistribution

A free-software license is a notice that grants the recipient of a piece of software extensive rights to modify and redistribute that software. These actions are usually prohibited by copyright law, but the rights-holder of a piece of software can remove these restrictions by accompanying the software with a software license which grants the recipient these rights. Software using such a license is free software as conferred by the copyright holder. Free-software licenses are applied to software in source code and also binary object-code form, as the copyright law recognizes both forms.

BSD licenses are a family of permissive free software licenses, imposing minimal restrictions on the use and distribution of covered software. This is in contrast to copyleft licenses, which have share-alike requirements. The original BSD license was used for its namesake, the Berkeley Software Distribution (BSD), a Unix-like operating system. The original version has since been revised, and its descendants are referred to as modified BSD licenses.

<span class="mw-page-title-main">Copyleft</span> Practice of mandating free use in all derivatives of a work

Copyleft is the legal technique of granting certain freedoms over copies of copyrighted works with the requirement that the same rights be preserved in derivative works. In this sense, freedoms refers to the use of the work for any purpose, and the ability to modify, copy, share, and redistribute the work, with or without a fee. Licenses which implement copyleft can be used to maintain copyright conditions for works ranging from computer software, to documents, art, scientific discoveries and even certain patents.

<span class="mw-page-title-main">GNU General Public License</span> Series of free software licenses

The GNU General Public License is a series of widely used free software licenses that guarantee end users the four freedoms to run, study, share, and modify the software. The license was the first copyleft for general use and was originally written by the founder of the Free Software Foundation (FSF), Richard Stallman, for the GNU Project. The license grants the recipients of a computer program the rights of the Free Software Definition. These GPL series are all copyleft licenses, which means that any derivative work must be distributed under the same or equivalent license terms. It is more restrictive than the Lesser General Public License and even further distinct from the more widely used permissive software licenses BSD, MIT, and Apache.

A free license or open license is a license which allows others to reuse another creator’s work as they wish. Without a special license, these uses are normally prohibited by copyright, patent or commercial license. Most free licenses are worldwide, royalty-free, non-exclusive, and perpetual. Free licenses are often the basis of crowdsourcing and crowdfunding projects.

Software relicensing is applied in open-source software development when software licenses of software modules are incompatible and are required to be compatible for a greater combined work. Licenses applied to software as copyrightable works, in source code as binary form, can contain contradictory clauses. These requirements can make it impossible to combine source code or content of several software works to create a new combined one.


  1. 1 2 3 New Media Rights (2008-09-12). "Open Source Licensing Guide". California Western School of Law .
  2. 1 2 "Top 20 licenses". Black Duck Software. 19 November 2015. Archived from the original on 19 July 2016. Retrieved 19 November 2015. 1. MIT license 24%, 2. GNU General Public License (GPL) 2.0 23%, 3. Apache License 16%, 4. GNU General Public License (GPL) 3.0 9%, 5. BSD License 2.0 (3-clause, New or Revised) License 6%, 6. GNU Lesser General Public License (LGPL) 2.1 5%, 7. Artistic License (Perl) 4%, 8. GNU Lesser General Public License (LGPL) 3.0 2%, 9. Microsoft Public License 2%, 10. Eclipse Public License (EPL) 2%
  3. 1 2 Balter, Ben (2015-03-09). "Open source license usage on". . Retrieved 2015-11-21. "1 MIT 44.69%, 2 Other 15.68%, 3 GPLv2 12.96%, 4 Apache 11.19%, 5 GPLv3 8.88%, 6 BSD 3-clause 4.53%, 7 Unlicense 1.87%, 8 BSD 2-clause 1.70%, 9 LGPLv3 1.30%, 10 AGPLv3 1.05%
  4. Free Software Foundation, Various Licenses and Comments about Them, GNU All-permissive License
  5. Information for Maintainers of GNU Software, License Notices for Other Files
  6. permissive on "A "permissive" license is simply a non-copyleft open-source license one that guarantees the freedoms to use, modify and redistribute, but that permits proprietary derivatives."
  7. Choosing an open-source license doesn't need to be scary on "Which of the following best describes your situation? I want it simple and permissive."
  8. "What is Copyleft". GNU. Retrieved 21 April 2011.
  9. "Categories of free and nonfree software".
  10. Amadeo, Ron (21 July 2018). "Google's iron grip on Android: Controlling open source by any means necessary". Ars Technica.
  11. With this in mind, the FreeBSD project advocates permissive licenses for companies and commercial use-cases: they say that they place only "minimal restrictions on future behavior" and argue that copyleft licenses are "legal time-bombs". See Montague, Bruce (2013-11-13). "Why you should use a BSD style license for your Open Source Project". FreeBSD . Retrieved 2015-11-28. 9. GPL Advantages and Disadvantages [..] 12. Conclusion
    In contrast to the GPL, which is designed to prevent the proprietary commercialization of open-source code, the BSD license places minimal restrictions on future behavior. This allows BSD code to remain open source or become integrated into commercial solutions, as a project's or company's needs change. In other words, the BSD license does not become a legal time-bomb at any point in the development process.

    In addition, since the BSD license does not come with the legal complexity of the GPL or LGPL licenses, it allows developers and companies to spend their time creating and promoting good code rather than worrying if that code violates licensing.
  12. 1 2 "Licence Compatibility". European Union Public Licence. Archived from the original on 2015-06-17. Retrieved 2015-05-30. The licenses for distributing free or open source software (FOSS) are divided in two families: permissive and copyleft. Permissive licenses (BSD, MIT, X11, Apache, Zope) are generally compatible and interoperable with most other licenses, tolerating to merge, combine or improve the covered code and to re-distribute it under many licenses (including non-free or "proprietary").
  13. 1 2 Hanwell, Marcus D. (2014-01-28). "Should I use a permissive license? Copyleft? Or something in the middle?". Retrieved 2015-05-30. Permissive licensing simplifies things One reason the business world, and more and more developers [...], favor permissive licenses is in the simplicity of reuse. The license usually only pertains to the source code that is licensed and makes no attempt to infer any conditions upon any other component, and because of this there is no need to define what constitutes a derived work. I have also never seen a license compatibility chart for permissive licenses; it seems that they are all compatible.
  14. "Frequently Asked Questions about the GNU Licenses Is GPLv3 compatible with GPLv2?". Retrieved 2014-06-03. No. Some of the requirements in GPLv3, such as the requirement to provide Installation Information, do not exist in GPLv2. As a result, the licenses are not compatible: if you tried to combine code released under both these licenses, you would violate section 6 of GPLv2. However, if code is released under GPL "version 2 or later," that is compatible with GPLv3 because GPLv3 is one of the options it permits.
  15. Landley, Rob. "CELF 2013 Toybox talk". Retrieved 2013-08-21. GPLv3 broke "the" GPL into incompatible forks that can't share code.
  16. "Interpreting, enforcing and changing the GNU GPL, as applied to combining Linux and ZFS". Retrieved 2020-06-08.
  17. US Copyright Office Form CO; see also Ashton-Tate v. Fox
  18. "OpenBSD Copyright Policy". The OpenBSD project. Retrieved 2020-06-09. In some jurisdictions, it is doubtful whether voluntarily placing one's own work into the public domain is legally possible. For that reason, to make any substantial body of code free, it is preferable to state the copyright and put it under an ISC or BSD license instead of attempting to release it into the public domain.
  19. Hipp, D. Richard. "Why SQLite succeeded as a database". The Changelog. Also at the time I did not realize, having lived my whole life in the United States, which is, you know, under British common law, where the public domain is something that's recognized. I did not realize that there were a lot of jurisdictions in the world where it's difficult or impossible for someone to place their works in the public domain. I didn't know. So that's a complication.
  20. The Free-Libre / Open Source Software (FLOSS) License Slide by David A. Wheeler on October 4, 2021
  21. Haff, Gordon. "The mysterious history of the MIT License". Retrieved 2020-06-08. [There's] a good argument to be made that the MIT License, also called the X Consortium or X11 License at the time, crystallized with X11 in 1987, and that's the best date to use. You could argue it was created in 1985 with possible adjustments over the next couple of years.
  22. Vaughan-Nichols, Steven J. "The fall of GPL and the rise of permissive open-source licenses". Retrieved 2015-11-28. The GPL is still the world's most popular open-source license but it's declining in use, while permissive licenses are gaining more fans, and some developers are choosing to release code without any license at all.
  23. Ronacher, Armin (2013-07-23). "Licensing in a Post Copyright World". Retrieved 2015-11-18.
  24. Aslett, Matthew (2011-06-06). "The trend towards permissive licensing". Archived from the original on 2015-10-13. Retrieved 2015-11-28.
  25. Does your code need a license? Posted 02 May 2013 by Jason Hibbets "Q: Are there software-development companies favoring a certain open-source license over another? What is the trend in the community? A: We're definitely seeing some trends away from copyleft licenses—mostly towards permissive licenses"
  26. 1 2 "Frequently Asked Questions | Open Source Initiative". Open Source Initiative . Retrieved 2022-08-09. A 'permissive' license is simply a non-copyleft open source license
  27. "Copyleft versus non-copyleft licenses in free / open source software". Qoppa Software. 2014-11-21. Retrieved 2022-08-09.
  28. Sen, Ravi; Subramaniam, Chandrasekar; Nelson, Matthew L. (2011). "Open Source Software Licenses: Strong-Copyleft, Non-Copyleft, or Somewhere in Between?". Decision Support Systems. 52 (1): 199–206. doi:10.1016/j.dss.2011.07.004. ISSN   0167-9236 . Retrieved 2022-08-09.
  29. 1 2 "Add Kirk's comment about "copycenter"; it's just too good to pass up". Historical FreeBSD fortune(6) database. Retrieved 2020-06-08.
  30. Raymond, Eric S. "copycenter". The Jargon File.
  31. 1 2 Stallman, Richard (2016-02-08). "License Compatibility and Relicensing". Free Software Foundation . Retrieved 2019-09-29. In general, lax permissive licenses (modified BSD, X11, Expat, Apache, Python, etc.) are compatible with each other. That's because they have no requirements about other code that is added to the program. They even permit putting the entire program (perhaps with changes) into a proprietary software product; thus, we call them "pushover licenses" because they can't say "no" when one user tries to deny freedom to others.
  32. How to choose a license for your own work Free Software Foundation
  33. 1 2 Smith, Luke, Why I Use the GPL and Not Cuck Licenses, Why be mean and bully BSD and MIT licenses calling them "Cuck Licenses"? Quite simply, using them is precisely analogous to being cuckolded. When you really look at it, the similarity is uncanny.
  34. "Re-assessing Copyleft vs Cuck Licenses". DAI-SOS Brigade. 2 February 2022.
  35. "Cuck license". InstallGentoo Wiki. A Cuck License is a permissive software license that that does not enforce the freedom of derivative works. This means that anyone can take software licensed under a Cuck License and turn it into proprietary software, effectively cucking the original author. Examples of Cuck Licenses are the MIT license and BSD license.