There are also Shared Source licenses which have some similarities with open source, but a number of critical differences make such licenses incompatible with the Open Source Definition.
Some software licenses define an Open Standard basis and may or may not be similar to open source, like some versions of Solaris and PGP .
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 2005 :
Open Source Licensing — a review and discussion of Lawrence Rosen's book ''Open Source Licensing: Software Freedom and Intellectual Property Law'' (ISBN 0131487876) on Slashdot
