Steve Ballmer wants to see all open source development done on Windows, not Linux. I wonder if this is out of love for open source or out of hatred for Linux. I guess that is the reason Microsoft is opening up .Net, sorry, releasing .Net. I am sure Microsoft knows that open source fosters open source.
Let us not nitpick. Microsoft has had immense number of opportunities to encourage open source, but it has not done so. Good open source development is quite active on Windows. Unfortunately it is not by or for Microsoft.
Maybe that is what Microsoft is looking for, not open source on Windows but open source for Microsoft.