As one of those "old schoolers" I don't view MS as any less evil than they used to be.

But they aren't the only 800 pound gorilla in the room - open source, google, apple, amazon have all taken a big chunk out of what MS was.

What prevents MS (or any one who acquires GitHub) from pulling a sourceforge? Well nothing prevents them, and I can't name someone who wouldn't want to monetize it -- that latter fact is going to be what kills the product/project.