The Open Source Initiative (OSI), the organization responsible for maintaining the definition of open source and evaluating open source licenses, has officially approved the Microsoft Community (Ms-CL) and Permissive (Ms-PL) licenses.

Microsoft submitted its Shared Source licenses shortly after announcing plans to do so at the O'Reilly Open Source Convention earlier this year. OSI president Michael Tiemann responded by pointing out that three of Microsoft's five Shared Source licenses impose restrictions that are clearly inconsistent with the Open Source definition, but acknowledged that the two licenses submitted by Microsoft had merit and would be evaluated.

"The decision to approve was informed by the overwhelming (though not unanimous) consensus from the open-source community that these licenses satisfied the 10 criteria of the Open Source definition, and should therefore be approved," said OSI in a statement. "Microsoft came to the OSI and submitted their licenses according to the published policies and procedures that dozens of other parties have followed over the years. Microsoft didn't ask for special treatment, and didn't receive any. In spite of recent negative interactions between Microsoft and the open-source community, the spirit of the dialog was constructive and we hope that carries forward to a constructive outcome as well."

OSI's decision to approve the Ms-PL and Ms-CL (also known as the Microsoft Reciprocal License) is unsurprising, since the Free Software Foundation's European branch has already voiced support for the licenses, publicly congratulated Microsoft for creating them, and expressed appreciation for the similarities between the Ms-CL and the FSF's own GPL license.

Despite receiving the praise of FSF Europe, Microsoft's open-source licenses have been widely criticized. Critics are concerned that Microsoft is trying to muddy the waters by obfuscating the distinction between its open-source licenses and its more restrictive shared-source licenses. The incompatibility between Microsoft's open source licenses and other prominent open source licenses is also a point of contention, since critics argue that it contributes to needless license proliferation, which contributes to fragmentation of the open-source ecosystem. This last criticism is also applicable to open-source licenses created by many other companies, like Sun's CDDL for instance.

Despite the problematic nature of license proliferation, the open source community would benefit considerably if Microsoft were to release more source code under these licenses. Microsoft has already released the Dynamic Language Runtime (DLR) for .NET under the Ms-PL, which means that it can be included in the open-source Mono .NET runtime and used in Novell's open source Silverlight implementation. It should be noted that the source code Microsoft recently released for the .NET Framework Libraries is distributed under the highly restrictive Microsoft Reference License, which is not an open-source license and doesn't facilitate redistribution. Microsoft will hopefully take this opportunity to demonstrate its willingness to promote open source .NET development by relicensing the .NET Framework Libraries under one of the company's OSI-approved licenses.

Although OSI validation of Microsoft's licenses is a very big win for Microsoft and the open-source software community, this victory is overshadowed by Microsoft's aggressive attitude towards open-source software. Certain vocal factions of the OSS community will express extreme distrust for Microsoft's open-source licenses, which will make it difficult for the company to build a bridge with the broader OSS community. Microsoft's unsubstantiated patent threats and blatantly dishonest studies don't help the situation.