it's a ploy by microsoft to "accidently" release their source code so that open source programmers see it. Anything these open source writers write in the future will be scrutinized by the microsoft attorney spanish inquisition for copyright infringment, and will make them unhireable. It's actually a brilliant strategy, so I'm convinced microsoft didn't mean to do it. The code tree for NT and the like has to be enormous though, I doubt the entire thing is just prancing around the internet.