Oh, the drama! The "key rival", the "worst enemy"! Bah. Online journalism is really at an all time low...
Anyways, you don't just hire someone. You put down an offer and, if the person is actually interested in working for you, he accepts it. There's no obligation to do that and the onus ALWAYS falls on the employee shoulders, after all, he could have refused the
offer very easily.
On the other hand... Munich doesn't seem to be doing that well with their Linux implementation. An implementation that, it needs to be remembered, was supposed to have a VM (probably VMWare) and a Windows license running on most of the "converted" machines.
So it was just a PR snag for Microsoft, as they would have sold lots of linceses anyways.