As I understand it Microsoft is now shipping a Linux kernel which they'll be maintaining themselves. I don't think this is really much to worry about, especially if it's a server only thing. Desktop is where their monopoly is, and where they could do more damage if they embraced Linux, then extended and extinguished.

Really this is just Microsoft being dragged backwards by the shirt collar into the 21st century. Probably they don't like Linux much and the GPL even less (Gates said as much on various occasions). But the contemporary reality on servers is either embrace Linux (the kernel, at a minimum) or just be irrelevant.