well, it's worth noting that since microsoft is also releasing the source code, the same thing could have happened with GPL. Though I suspect the author would be even less happy if they had done all the same stuff (minus removing the copyright notice, even) and then not released the source, so that's not me arguing against the GPL
I also think in practice microsoft would have been less likely to actually take the code, and probably would just have reimplemented the ideas in it if it was GPL