About Open Source Licenses
Open source licenses are licenses that comply with the Open Source Definition — in brief, they allow software to be freely used, modified, and shared. To be approved by the Open Source Initiative (also known as the OSI), a license must go through the Open Source Initiative’s license review process.
The following OSI-approved licenses are popular, widely used, or have strong communities (as defined in the 2006 Proliferation Report):
- Apache License 2.0
- BSD 3-Clause “New” or “Revised” license
- BSD 2-Clause “Simplified” or “FreeBSD” license
- GNU General Public License (GPL)
- GNU Library or “Lesser” General Public License (LGPL)
- MIT license
- Mozilla Public License 2.0
- Common Development and Distribution License
- Eclipse Public License
All Approved Licenses
Many other licenses are also OSI-approved, but fall into other categories, such as special-purpose licenses, superseded licenses, or retired licenses. Complete lists that include all approved licenses are available:
The OSI maintains a FAQ, which includes a lot of useful background on open source licensing, including:
- Can Open Source software be used for commercial purposes?
- What is “free software” and is it the same as “open source”?
- What is “copyleft”? Is it the same as “open source”?
- What is a “permissive” Open Source license?
- Which Open Source license should I choose to release my software under?
- Is <SOME PROGRAM> Open Source?
- Can I call my program “Open Source” even if I don’t use an approved license?
- Is <SOME LICENSE> an Open Source license, even if it is not listed on your web site?
For more information about open source licenses and in particular about the Open Source Initiative’s approval process, see: