I don't quite know why you think were Open Source friendly from; while iD have indeed released older engines as open source for some time they were closed to the point where you weren't allowed to use their tools to create levels for your own game. Valve have no Open Source pedigree that I can think of; they might put out some papers but I can't ever recall them throwing source out into the open.
They are open source friendly, just because you don't release your whole code base doesn't mean you hate open source. The guys behind these companies have always worked with open source projects, like improving open driver compatibility, even now valve is working with linux programmers on many projects. They are not going to throw their hard work out in the open, that would be stupid man. They are smart about it and fund projects that write patches for open source projects of all types.