Open Source Weblog

Microsoft has five shared source licenses, two of which would have the potential to be approved by the OSI.

The Microsoft Permissive License (Ms-PL) is the least restrictive and could be thought of as the most like the BSD license in that it allows users to view, modify, and redistribute the source code for either commercial or non-commercial purposes.

The Microsoft Community License (Ms-CL) is more like the GNU General Public License, in that it allows users to view, modify, and redistribute the code and ensures that any larger work distributed as a single file also needs to be licensed under the same license.

The Microsoft Reference License (Ms-RL) is a reference-only license that allows users to view the source code but not modify or redistribute it and therefore stands no chance of being approved.

The other two licenses, the Ms-LPL and Ms-LCL, are limited versions that only allow code to be run on the Windows operating system, and would therefore fail to meet the criteria of the Open Source Definition.

When the licenses were introduced in late 2005, the Free Software Foundation Europe noted that the Ms-PL and Ms-CL appeared to satisfy the four freedoms that define Free Software.

That would give the licenses a good chance of meeting the 10 requirements that make up the Open Source Definition, but there are no guarantees. Even if the license were found to have met all 10 criteria, the OSI has been actively trying to reduce license proliferation and it could be that Microsoft’s licenses are seen as too similar to existing licenses to warrant separate approval.