License compatibility
Encyclopedia
License compatibility refers to the problem with licenses applied to works subject to copyright, particularly licenses of software packages, which can contain contradictory requirements, rendering it impossible to combine source code
from such packages or content from such works in order to create new works.
For example, suppose one license says "modified versions must mention the developers in any advertising materials", and another license says "modified versions cannot contain additional attribution requirements". If someone combined a software package which uses one license with a software package which uses the other, it would be impossible to legally distribute the combination without direct permission from the copyright holders for both packages because the two requirements cannot be simultaneously fulfilled. Thus, these two packages would be license-incompatible.
Not all licenses approved by OSI
or by the Free Software Foundation
are compatible with each other, thus not all the code under OSI or FSF approved licenses can be mixed. For example new software which mixes code released under the Mozilla Public License
with code under the GNU General Public License
(both licenses are OSI and FSF approved) cannot be distributed in a way which does not violate the terms of the GPL or the MPL. The FLOSS License Slide shows if some common licenses are compatible.
has argued that GPL compatibility is an important feature of software licenses. Many of the most common free software licenses, such as the original MIT/X license
, BSD licenses
(in the three-clause and two-clause forms, though not the original four-clause form), and the LGPL
, are "GPL-compatible". That is, their code can be combined with a program under the GPL without conflict (the new combination would have the GPL applied to the whole). When it comes to copyleft
software licenses, they are not inherent GPL-compatible but some has exception clauses that allows combining software that is under different licenses or license versions.
Source code
In computer science, source code is text written using the format and syntax of the programming language that it is being written in. Such a language is specially designed to facilitate the work of computer programmers, who specify the actions to be performed by a computer mostly by writing source...
from such packages or content from such works in order to create new works.
For example, suppose one license says "modified versions must mention the developers in any advertising materials", and another license says "modified versions cannot contain additional attribution requirements". If someone combined a software package which uses one license with a software package which uses the other, it would be impossible to legally distribute the combination without direct permission from the copyright holders for both packages because the two requirements cannot be simultaneously fulfilled. Thus, these two packages would be license-incompatible.
Not all licenses approved by OSI
Open Source Initiative
The Open Source Initiative is an organization dedicated to promoting open source software.The organization was founded in February 1998, by Bruce Perens and Eric S. Raymond, prompted by Netscape Communications Corporation publishing the source code for its flagship Netscape Communicator product...
or by the Free Software Foundation
Free Software Foundation
The Free Software Foundation is a non-profit corporation founded by Richard Stallman on 4 October 1985 to support the free software movement, a copyleft-based movement which aims to promote the universal freedom to create, distribute and modify computer software...
are compatible with each other, thus not all the code under OSI or FSF approved licenses can be mixed. For example new software which mixes code released under the Mozilla Public License
Mozilla Public License
The Mozilla Public License is a free and open source software license. Version 1.0 was developed by Mitchell Baker when she worked as a lawyer at Netscape Communications Corporation and version 1.1 at the Mozilla Foundation...
with code under the GNU General Public License
GNU General Public License
The GNU General Public License is the most widely used free software license, originally written by Richard Stallman for the GNU Project....
(both licenses are OSI and FSF approved) cannot be distributed in a way which does not violate the terms of the GPL or the MPL. The FLOSS License Slide shows if some common licenses are compatible.
GPL compatibility
David A. WheelerDavid A. Wheeler
David A. Wheeler is a computer scientist. He is best known for his work on Open source software/Free-libre software and Computer security.-Open Source Software:...
has argued that GPL compatibility is an important feature of software licenses. Many of the most common free software licenses, such as the original MIT/X license
MIT License
The MIT License is a free software license originating at the Massachusetts Institute of Technology . It is a permissive license, meaning that it permits reuse within proprietary software provided all copies of the licensed software include a copy of the MIT License terms...
, BSD licenses
BSD licenses
BSD licenses are a family of permissive free software licenses. The original license was used for the Berkeley Software Distribution , a Unix-like operating system after which it is named....
(in the three-clause and two-clause forms, though not the original four-clause form), and the LGPL
GNU Lesser General Public License
The GNU Lesser General Public License or LGPL is a free software license published by the Free Software Foundation . It was designed as a compromise between the strong-copyleft GNU General Public License or GPL and permissive licenses such as the BSD licenses and the MIT License...
, are "GPL-compatible". That is, their code can be combined with a program under the GPL without conflict (the new combination would have the GPL applied to the whole). When it comes to copyleft
Copyleft
Copyleft is a play on the word copyright to describe the practice of using copyright law to offer the right to distribute copies and modified versions of a work and requiring that the same rights be preserved in modified versions of the work...
software licenses, they are not inherent GPL-compatible but some has exception clauses that allows combining software that is under different licenses or license versions.
See also
- List of FSF approved software licenses
- License proliferationLicense proliferationLicense proliferation refers to the problems created when additional software licenses are written for software packages. License proliferation affects the free software community. Often when a software developer would like to merge portions of different software programs they are unable to do so...
- Backward compatibilityBackward compatibilityIn the context of telecommunications and computing, a device or technology is said to be backward or downward compatible if it can work with input generated by an older device...
- Forward compatibilityForward compatibilityForward compatibility or upward compatibility is a compatibility concept for systems design, as e.g. backward compatibility. Forward compatibility aims at the ability of a design to gracefully accept input intended for later versions of itself...