Getting Shit Done trumps all things. The reality as well is that the majority of the .Net platform (with the exception of the Standard Libraries, I believe) are open ECMA Standards (See among others, #335).
Unlike .NET, Java has a free implementation (OpenJDK) and any code derived from OpenJDK is granted Java patents. Apache is a different story as they are developing a Java implementation under permissive license, which means that Apache code could be used in non-free software (including .NET), that would make Java vulnerable to the "Embrace, Extend and Extinguish" strategy. That is what Apache is paid for by Microsoft.
So my point is that supporting .NET is bad for the ideals of the free software community, yet it is good for pragmatic reasons as it could bring more users. And I have a strong impression that today pragmatism is favored over principle by the community, the decline of copyleft is also a sign of that.