Josh Holmes tells some of the story of how open source--and even contribution--came to Microsoft. Worth a listen.
"My full-time job is writing open source software ... at Microsoft." Josh Holmes, Director of Architecture, Microsoft Partner Catalyst Team, has one of the coolest jobs I can think of in the IT and startup worlds. He runs a large team of top notch engineers whose mission it is to help startups with hard technology problems. And they help them by fixing, improving, and contributing to open source tools that they need. Yes, this is a Microsoft job. Yes, everything they work on is contributed back to open source projects. Really.
https://dev.acquia.com/podcast/198-embracing-and-contributing-open-source-microsoft