All open-source projects that deal with reimplementing parts of Windows, particularly Wine and ReactOS, consider those leaked sources radioactive and would not accept any patches if there's even a slightest suspicion that the patch author gleaned anything from those sources. Those same sources officially released under an open-source license would change that.
I wouldn’t assume Microsoft execs view increased capabilities to run windows programs in Linux as a bad thing, when they think about the matter at all. They would certainly prefer that such a capability be developed by someone else, so they don’t have to support it.