Maybe my ignorance is showing, but I've felt like Apple has been the least involved major company of them all when it comes to community stuff. They feel so aloof to me. My impression is Microsoft used to be that way but is changing.
Also LLVM. Apple heavily funded work on it, and it's now used by everybody who's anybody in the industry, from Google to MS.
Apple just doesn't care to go into much community development by committee (bazaar) because they have their own (cathedral-like) agenda to follow.
Also: WebKit, Objective-C. (debatable since the GPL forced their hand)