In a board meeting held October 10th, and announced today, the Open Source Initiative approved two of Microsoft's software licenses: the Microsoft Reciprocal License and the Microsoft Public License. These licenses are refreshingly short and clean, compared to, say, the GPLv3 and the Sun CDDL. Like Larry Rosen's pair of licenses (the Academic Free License and Open Software License), they share a patent peace clause, a no-trademark-license clause, and they differ between each other only in the essential clause of reciprocation.
Of course, Microsoft is not widely trusted in the Open Source world, and their motives have been called into question during the approval discussions. How can they be attacking Open Source projects on one hand, and seeking not only to use open source methods, but use of the OSI Approved Open Source trademark? Nobody knows for sure except for Microsoft. But if you are confident that Open Source is the best way to develop software (as we at the Open Source Initiative are), then you can see why Microsoft would both attack Open Source and seek to use it at the same time. It is both their salvation and their enemy.