The Roslyn project, F#, Docker integration, MS Band etc clearly show that MS has learned it's lessons and are responsible citizens of OSS world.
Kudos Microsoft.
"Plays well with others. We've established partnerships with key service providers who embrace our vision of healthier living. And we're open to even more. Microsoft Health as a platform will be strengthened by broader collaboration from device and service partners. See how connecting to the partners we have today can make your Microsoft Band experience even more amazing."
I will perhaps re-iterate my thoughts once Ms stop extorting Android device manufacturers for BS software patents. Until then, I am not touching anything from them.
To answer your question, Microsoft is not only about mobile. Their work on Roslyn compiler, F#, Reactive Extensions, SignalR, ASP.Net vNext etc is high quality open source. Moreover if they make their tools open and play nice with Android/iOS etc, we all win, right?