I don't think MS is "embracing open source" (or even necessarily rejecting it), so much as they are acknowledging that Linux servers are here to stay for a while, and simply grabbing a piece of the pie instead of ignoring it. Much like Oracle having its own Linux distro.

Perhaps enough shareholders complained about a market segment simply being given to OSX (development environment for work intended for a POSIX server) that they simply had to act. No more, no less. Not benevolent or malevolent, just picking up some loose cash :-)