What a strange world we live in.
What's changed for Microsoft and open source in recent years is Microsoft has refocused on solving both its own and customers' business problems. That means, first, Linux is treated as an equal to Windows. "Microsoft actually uses a lot of Linux in-house. It's no longer everything has to be run on Windows internally." Microsoft is doing this because "We're solving business problems and we're very pragmatic."
The Marriage of Microsoft and Linux by Steven J. Vaughan-Nichols