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To be fair apple's CUPS is pretty critical for printing under linux.

And then there is webkit.

To be more fair Webkit started as a fork of some of KDE's libraries.

Yeah, but it's being used, and developed, a hell of a lot more now than it was as part of KDE.

Apple bought CUPS

Google bought X.

X being pretty much everything they do besides Search. Not sure if that is much of an argument.