Software relicensing is applied inopen-sourcesoftware development whensoftware licenses of software modules areincompatible and are required to be compatible for a greater combined work. Licenses applied to software ascopyrightable works, in source code as binary form,[1] can contain contradictory clauses. These requirements can make it impossible to combinesource code or content of several software works to create a new combined one.[2][3]
Sometimes open-source software projects get stuck in a license incompatibility situation. Often the only feasible way to resolve this situation is re-licensing of all participating software parts. For successful relicensing the agreement of all involved copyright holders, typically the developers, to a changed license is required. While in thefree and open-source domain achieving 100% coverage of all authors is often impossible due to the many contributors involved, often it is assumed that a great majority is sufficient. For instance,Mozilla assumed an author coverage of 95% to be sufficient.[4] Others in the free and open-source software (FOSS) domain, such asEric S. Raymond, came to different conclusions regarding the requirements for relicensing of a whole code base.[5]
An early example of anopen-source project that did successfully re-license for license compatibility reasons is theMozilla project and theirFirefox browser. Thesource code ofNetscape'sCommunicator 4.0 browser was originally released in 1998 under theNetscape Public License/Mozilla Public License[6] but was criticised by theFSF andOSI for being incompatible.[7][8] Around 2001Time Warner, exercising its rights under the Netscape Public License, and at the request of the Mozilla Foundation, relicensed[9] all code in Mozilla that was under the Netscape Public License (including code by other contributors) to an MPL 1.1/GPL 2.0/LGPL 2.1tri-license, thus achieving GPL-compatibility.[10]
TheVorbis library was originally licensed as LGPL, but in 2001 the license was changed to theBSD license with endorsement ofRichard Stallman to encourage adoption.[11][12]
TheVLC project also has a complicated license history due to license compatibility: in 2007 it decided for license compatibility reasons to not upgrade to the just releasedGPLv3.[13] After VLC was removed fromApple App Store at the beginning of 2011, in October 2011 the VLC project re-licensed the VLC library part from the GPLv2 to the LGPLv2 to achieve better compatibility.[14][15] In July 2013 the VLC application could then be resubmitted to theiOS App Store relicensed under the Mozilla Public License.[16]
7-Zip'sLZMA SDK, originally dual-licensed under both theGNU LGPL andCommon Public License,[17] with an additional special exception for linked binaries, was placed byIgor Pavlov in thepublic domain on December 2, 2008.[18]
TheGNU TLS project adopted the LGPLv3 license in 2011 but in 2013 relicensed their code back to LGPLv2.1 due to serious license compatibility problems.[19][20][21]
TheGNU Free Documentation License in version 1.2 is not compatible with the widely usedCreative Commons Attribution-ShareAlike license, which was a problem, for instance, for theWikipedia.[22] Therefore, at the request of theWikimedia Foundation, the FSF added, with version 1.3 of the GFDL, a time-limited section allowing specific types of websites using the GFDL to additionally offer their work under the CC BY-SA license.[23] Following in June 2009, the Wikimedia Foundation migrated their projects (Wikipedia, etc.) bydual licensing to theCreative Commons Attribution-ShareAlike as main license, additional to the previously usedGFDL.[24] An improved license compatibility with the greaterfree content ecosystem was given as reason for the license change.[25][26]
In 2010 theOGRE project changed their license from the LGPL to theMIT License; a simpler license text was given as reason.[27][28][29]
Another case was the relicensing of GPLv2 licensedLinux kernel header files to the BSD license byGoogle for theirAndroid libraryBionic. To get rid of the GPL, Google claimed that theheader files were cleaned from any copyright-able work, reducing them to non-copyrightable "facts".[30][31] This interpretation was challenged for instance by Raymond Nimmer, a law professor at theUniversity of Houston Law Center.[32]
In November 2013POV-Ray was relicensed under theGNU Affero General Public License version 3 (or later),[33] after being distributed since 1991 under a FOSS-incompatible, non-commercialsource available customPOV-Ray license.[34][35] POV-Ray was developed before FOSS licenses became widely used, therefore the developers wrote their own license which became later a problem due to license incompatibility with the FOSS ecosystem.
In 2014, theFreeCAD project changed their license from GPL to LGPLv2 due to GPLv3/GPLv2 incompatibilities.[36][37]
In 2014Gang Garrison 2 relicensed from GPLv3 toMPL for improved library compatibility.[38][39]
In May 2015 theDolphin project changed its license from "GPLv2 only" to "GPLv2 or any later" for better compatibility.[40]
In June 2015mpv started the relicensation process of the project's GPL licensed source code for improved license compatibility under LGPLv2 by getting consent from the majority (95%+) of the contributing developers.[41] In August 2016 approx. 90% of the authors could be reached and consented. In October 2017 the switch was finalized.[42]
In July 2015Seafile switched for improved license compatibility, especially withGit, from the GPLv3 to the GPLv2.[43][44]
In 2015Natron was relicensed from MPL to theGPLv2 to allow better commercialization.[45]
In 2016MAME achieved a relicensing of the code base to BSD/GPL[46] after struggling for years with an own written custom license, with non-commercial license terms.[47][48][49][50]
In August 2016 theMariaDB Corporation relicensed the database proxy server MaxScale from GPL to the non-FOSS but source-available and time-limitedBusiness source license (BSL)[51] which defaults back after three years to GPL.[52][53] In 2017 followed version 1.1, revised with feedback also fromBruce Perens.[54][55]
For a long timeD back-endsource code was available but under a non-open source conformlicense,[56] because it was partially developed atSymantec and couldn't be relicensed as open source.[57] On April 9, 2017, also the back-end part could be relicensed to the open-sourceBoost Software License.[58][59][60]
On July 27, 2017Microsoft Research changed the license of space combat simulatorAllegiance from the MSRshared source license,[61] under which the game was opened in 2004,[62] to the MIT license.[63][64]
Someone who works with many lawyers on free software copyright issues later told me that it is not necessary to get permission from 100% of the copyright holders. It would suffice if there was permission from the copyright holders of 95% of the source code and no objections from the holders of the other 5%. This, I'm told, is how Mozilla was able to relicense to the GPL in 2003 despite years of community contributions.
Some time ago mozilla.org announced its intent to seek relicensing of Mozilla code under a new licensing scheme that would address perceived incompatibilities of the Mozilla Public License (MPL) with the GNU General Public License (GPL) and GNU Lesser General Public License (LGPL).
In 2001, VLC was released under the OSI-approved GNU General Public version 2, with the commonly-offered option to use "any later version" thereof (though there was not any such later version at the time). Following the release by the Free Software Foundation (FSF) of the new version 3 of its GNU General Public License (GPL) on the 29th of June 2007, contributors to the VLC media player, and other software projects hosted at videolan.org, debated the possibility of updating the licensing terms for future version of the VLC media player and other hosted projects, to version 3 of the GPL. [...] There is strong concern that these new additional requirements might not match the industrial and economic reality of our time, especially in the market of consumer electronics. It is our belief that changing our licensing terms to GPL version 3 would currently not be in the best interest of our community as a whole. Consequently, we plan to keep distributing future versions of VLC media player under the terms of the GPL version 2. [...]we will continue to distribute the VLC media player source code under GPL "version 2 or any later version" until further notice.
LGPLv3 is the latest version of the GNU Lesser General Public License. It follows the successful LGPLv2.1 license, and was released by Free Software Foundation as a counterpart to its GNU General Public License version 3. The goal of the GNU Lesser General Public Licenses is to provide software that can be used by both proprietary and free software. This goal has been successfully handled so far by LGPLv2.1, and there is a multitude of libraries using that license. Now we have LGPLv3 as the latest, and the question is how successful is LGPLv3 on this goal? In my opinion, very little. If we assume that its primary goal is to be used by free software, then it blatantly fails that.
Starting with version 3.7, POV-Ray is released under the AGPL3 (or later) license and thus is Free Software according to the FSF definition. […] Full source code is available, allowing users to build their own versions and for developers to incorporate portions or all of the POV-Ray source into their own software provided it is distributed under a compatible license (for example, the AGPL3 or – at their option – any later version).
[...]the unfortunate situation with support for DWG files in free CAD software via LibreDWG. We feel, by now it ought to be closed. We have the final answer from FSF. [...] "We are not going to change the license."
Licences used in FreeCAD - FreeCAD uses two different licenses, one for the application itself, and one for the documentation: Lesser General Public Licence, version 2 or superior (LGPL2+) […] Open Publication Licence
tl;dr: The current license prevents us from using certain nice and (cost-)free libraries / frameworks, so we want to change it. The new license (MPL) would be strictly more free than the old one, and is the same one that's also used by Firefox.
Microsoft Corporation ("Microsoft") hereby relicenses the Microsoft Video Game Allegiance source code found athttps://github.com/FreeAllegiance/Allegiance/tree/master/src ("Allegiance Source Code") from the current Microsoft Research Shared Source license Agreement (MSR-SSLA) to the MIT license.
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