I happened to come across this article in Redmond Developer News recently…
Redmond Among Contributors to Open Source PHP Framework
…about contributers to the Zend Framework. Among the many (400) contributers to the project are Google and Microsoft. It’s probably just me, but I found it amusing (in a good way) that the two arch-rivals contributed pieces to the same Open Source project.
The article goes on to describe how Microsoft sponsored work to enable InfoCard (now called CardSpace) support in a number of Open Source products including Zend and Ruby on Rails.
I don't think this is anything new.
Microsoft spent a chunk of change to support a company called ActiveState a few years back (about 10). Back then it looked like Perl was going to take over the world :-D ActiveState, you may have heard of them, make Perl and Perl development tools.