Free 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 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.
An open-source license is a type of license for computer software and other products that allows the source code, blueprint or design to be used, modified and/or shared under defined terms and conditions. This allows end users and commercial companies to review and modify the source code, blueprint or design for their own customization, curiosity or troubleshooting needs. Open-source licensed software is mostly available free of charge, though this does not necessarily have to be the case.
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 Open Software License (OSL) is a software license created by Lawrence Rosen. The Open Source Initiative (OSI) has certified it as an open-source license, but the Debian project judged version 1.1 to be incompatible with the DFSG. The OSL is a copyleft license, with a termination clause triggered by filing a lawsuit alleging patent infringement.
Open-source software (OSS) is computer software that is released under a license in which the copyright holder grants users the rights to use, study, change, and distribute the software and its source code to anyone and for any purpose. Open-source software may be developed in a collaborative public manner. Open-source software is a prominent example of open collaboration, meaning any capable user is able to participate online in development, making the number of possible contributors indefinite. The ability to examine the code facilitates public trust in the software.
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.
Alternative terms for free software, such as open source, FOSS, and FLOSS, have been a controversial issue among free and open-source software users from the late 1990s onwards. These terms share almost identical licence criteria and development practices.
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.
The PHP License is the software license under which the PHP scripting language is released. The PHP License is designed to encourage widespread adoption of the source code. Redistribution is permitted in source or binary form with or without modifications, with some caveats.
WTFPL is a permissive free software license, compatible with the GNU GPL. As a public domain like license, the WTFPL is essentially the same as dedication to the public domain. It allows redistribution and modification of the work under any terms. The title is an abbreviation of "Do What The Fuck You Want To Public License".
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.
The University of Illinois/NCSA Open Source License, or UIUC license, is a permissive free software license, based on the MIT/X11 license and the 3-clause BSD license. By combining parts of these two licenses, it attempts to be clearer and more concise than either.
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 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.
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.
Copyleft is the practice of granting the right to freely distribute and modify intellectual property with the requirement that the same rights be preserved in derivative works created from that property. Copyleft in the form of licenses can be used to maintain copyright conditions for works ranging from computer software, to documents, art, scientific discoveries and even certain patents. Copyleft is an arrangement whereby software or artistic work may be used, modified, and distributed freely on condition that anything derived from it is bound by the same conditions.
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 were originally written by the founder of the Free Software Foundation (FSF), Richard Stallman, for the GNU Project. The license grant 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.
The Shared Source Initiative (SSI) is a source-available software licensing scheme launched by Microsoft in May 2001. The program includes a spectrum of technologies and licenses, and most of its source code offerings are available for download after eligibility criteria are met.
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.
