An open-source license is a copyright license for computer software that follows the principles of the open source movement. More formally, a license is considered open-source when it has approved by the Open Source Initiative, with the criteria being the Open Source Definition. Software in the public domain (that is, with no copyright license at all), meets those criteria as long as all source code is made available, and is therefore recognized by the OSI and entitled to use their service mark.

In addition, OSI has approved the following licenses as of 2003:

Academic Free License
Apache Software License
Apple Public Source License
Artistic license
Common Public License
Eiffel Forum License
BSD License
GNU General Public License (GPL)
GNU Lesser General Public License (LGPL)
Historical Permission Notice and Disclaimer
IBM Public License
Intel Open Source License
Jabber Open Source License
MIT License
MITRE Collaborative Virtual Workspace License (CVW License)
Motosoto License
Mozilla Public License 1.0 (MPL)
Mozilla Public License 1.1 (MPL 1.1)
NetHack General Public License
Nokia Open Source License
Open Software License
Open Group Test Suite License
Python license
Python Software Foundation License
Qt Public License (QPL)
Ricoh Source Code Public License
Sleepycat License
Sun Industry Standards Source License (SISSL)
Sun Public License
Vovida Software License v. 1.0
W3C License
X.Net License
zlib-libpng license
Zope Public License

It should be noted that the Free Software Foundation has different criteria for evaluating whether or not a license qualifies a program as free software. See Free software license.