This post by John Lam, highlights the change of tide at Microsoft. The company is actively trying to court opensource, notable measures in this direction are:

• See the code – Opensourcing .NET framework
• Resources for interoperating – The Opensource interoperability lab
• Support opensource – The Dynamic Languages Runtime

Well, you might argue that these are tactical moves and not a strategy. I let that be dictated by time and persuasion ….