What would happen if Gates opened up a "hardware" company and didn't allow anyone to use his "windows" but his company? OR IF he integrated Zune software into Windows Media player? uhh huh... we all know... but apple's allowed to do it..
OK... let's demand that Gates allow WMP with DRM to run on Apple's... or demand that Gates let Zune software run on Apple's and iPods.
Oh, by the way, it is INDEED illegal to run Windows on all those PCs... unless you buy a license from Microsoft. If you run it without permission from Microsoft then it is just as illegal as running OS X on that box without permission from Apple.
Even running Linux requires that you agree to the GNU License. It has a cost as well; you give up something when you agree to it.