FOSS stands for "Free and Open Source Software". There is no one universally agreed-upon definition of FOSS software and various groups maintain approved lists of licenses. The Open Source Initiative (OSI) is one such organization keeping a list of open-source licenses.[1] The Free Software Foundation (FSF) maintains a list of what it considers free.[2] FSF's free software and OSI's open-source licenses together are called FOSS licenses. There are licenses accepted by the OSI which are not free as per the Free Software Definition. The Open Source Definition allows for further restrictions like price, type of contribution and origin of the contribution, e.g. the case of the NASA Open Source Agreement, which requires the code to be "original" work.[3][4] The OSI does not endorse FSF license analysis (interpretation) as per their disclaimer.[5]
The FSF's Free Software Definition focuses on the user's unrestricted rights to use a program, to study and modify it, to copy it, and to redistribute it for any purpose, which are considered by the FSF the four essential freedoms.[6][7] The OSI's open-source criteria focuses on the availability of the source code and the advantages of an unrestricted and community driven development model.[8] Yet, many FOSS licenses, like the Apache License, and all Free Software licenses allow commercial use of FOSS components.[9]
The following table compares various features of each license and is a general guide to the terms and conditions of each license, based on seven subjects or categories. Recent tools like the European Commissions' Joinup Licensing Assistant,[10] makes possible the licenses selection and comparison based on more than 40 subjects or categories, with access to their SPDX identifier and full text. The table below lists the permissions and limitations regarding the following subjects:
Linking - linking of the licensed code with code licensed under a different license (e.g. when the code is provided as a library)
Distribution - distribution of the code to third parties
Modification - modification of the code by a licensee
Patent grant - protection of licensees from patent claims made by code contributors regarding their contribution, and protection of contributors from patent claims made by licensees
Private use - whether modification to the code must be shared with the community or may be used privately (e.g. internal use by a corporation)
Sublicensing - whether modified code may be licensed under a different license (for example a copyright) or must retain the same license under which it was provided
TM grant - use of trademarks associated with the licensed code or its contributors by a licensee
In this table, "permissive" means the software has minimal restrictions on how it can be used, modified, and redistributed, usually including a warranty disclaimer. "Copyleft" means the software requires that its source code be made publicly available and that all provisions in the license be preserved in derivative works.
This table lists for each license what organizations from the FOSS community have approved it – be it as a "free software" or as an "open source" license – , how those organizations categorize it, and the license compatibility between them for a combined or mixed derivative work. Organizations usually approve specific versions of software licenses. For instance, a FSF approval means that the Free Software Foundation (FSF) considers a license to be free-software license. The FSF recommends at least "Compatible with GPL" and preferably copyleft. The OSI recommends a mix of permissive and copyleft licenses, the Apache License 2.0, 2- & 3-clause BSD license, GPL, LGPL, MIT license, MPL 2.0, CDDL and EPL.
^The original version of the Artistic License is defined as non-free because it is overly vague, not because of the substance of the license. The FSF encourages projects to use the Clarified Artistic License instead.
^But can be made compatible by upgrading to GPLv3 via the optional "or later" clause added in most GPLv2 license texts.
^"Other Resources & Disclaimer". Open Source Initiative. While the OSI acknowledges these as potentially helpful resources for the community, it does not endorse any content, contributors or license interpretations from these websites.[...]The OSI does not promote or exclusively favor any of the above resources, but instead mentions them as a neutral, separate third-party.
^opensource.org/about "Open source is a development method for software that harnesses the power of distributed peer review and transparency of process. The promise of open source is better quality, higher reliability, more flexibility, lower cost, and an end to predatory vendor lock-in."
^Popp, Dr. Karl Michael (2015). Best Practices for commercial use of open source software. Norderstedt, Germany: Books on Demand. ISBN978-3738619096.
^Are GPLv2 and CDDL incompatible? on hansenpartnership.com by James E.J. Bottomley "What the above analysis shows is that even though we presumed combination of GPLv2 and CDDL works to be a technical violation, there's no way actually to prosecute such a violation because we can’t develop a convincing theory of harm resulting. Because this makes it impossible to take the case to court, effectively it must be concluded that the combination of GPLv2 and CDDL, provided you’re following a GPLv2 compliance regime for all the code, is allowable." (23 February 2016)
^"Frequently Answered Questions". opensource.org. 21 October 2007. CC0 was not explicitly rejected, but the License Review Committee was unable to reach consensus that it should be approved
^ ab"Frequently Asked Questions about the GNU Licenses – Is GPLv3 compatible with GPLv2?". gnu.org. Retrieved 3 June 2014. 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.
