Maybe not first class, but I think Microsoft's eaten a bit of humble pie (ala IBM ~15-20 years ago when they started ramping up Linux efforts) and generally playing nice.
Who ten years ago would have imagined so much of .NET would wind up MIT licensed, not just some 'shared source' malarky, on Sourceforge's ~2015 successor?
This isn't the Microsoft of the Halloween memos anymore.
No, we are making them first class. When we have a bug that breaks one of our three build queues (Windows, Linux, Mac), it will not be acceptable to break any of the platforms.