For apple I think the theme is engine / skin not what the license requires. osx : darwin :: safari : webkit Notice how the relationships revolve around the en

For apple I think the theme is engine / skin not what the license requires. osx : darwin :: safari : webkit Notice how the relationships revolve around the engine vs skin, not what the GPL requires. In other words, apple protects what makes them apple, not the underpinnings, at least in these examples.