Comparison of free and open-source software licenses
Understanding free and open-source software licenses
Free and Open Source Software (FOSS) has no single universal definition. Two main groups manage lists of licenses: the Free Software Foundation (FSF) for “free” software and the Open Source Initiative (OSI) for “open-source” software. Some licenses are approved by OSI but not by FSF, and vice versa.
What the definitions focus on
- FSF free software definition: four essential freedoms for users — run the program, study how it works, change it, and share copies.
- OSI open-source definition: emphasizes the availability of source code and a collaborative, community-driven development model.
How licenses are compared
- Many licenses are approved by both FSF and OSI; some are approved by one but not the other.
- Most licenses allow commercial use, including popular ones like Apache and many Free Software licenses.
- A simple, common comparison exists (free-software license comparison). Tools like the European Commission’s Licensing Assistant can compare licenses on many criteria and show their SPDX identifiers and full text.
Key ideas in license comparisons
- Permissive vs. copyleft: permissive licenses have few restrictions on use, modification, and redistribution; copyleft licenses require that derivative works also be shared under the same terms.
- The table in such comparisons shows what each license permits or restricts, which organizations have approved it, how they categorize it (free vs. open source), and how compatible it is with other licenses.
- Approvals usually apply to specific license versions. FSF approval means the license is considered free, and FSF often looks for compatibility with GPL and some form of copyleft. OSI approves a mix of permissive and copyleft licenses (examples include Apache 2.0, BSD licenses, GPL, LGPL, MIT, MPL 2.0, CDDL, and EPL).
This page was last edited on 2 February 2026, at 17:10 (CET).