1) Ability to unlock or root your device to run any OS
2) Having access to an open App Ecosystem.
The GNU license doesn't help with either of this issues. There are plenty of GNU/Android devices shipped with locked boot loaders. And nothing is stopping Google from locking down their App Store like Apples except a different corporate policy.
Note: I barely use Apple or Microsoft, so the question is NOT rhetorical.
http://en.wikipedia.org/wiki/OS_X
There you will find:
http://en.wikipedia.org/wiki/Comparison_of_BSD_operating_sys...
"... Apple Inc.'s iOS and Mac OS X, with its Darwin base including a large amount of code derived from FreeBSD."
http://en.wikipedia.org/wiki/Darwin_(operating_system)
"Darwin is an open source POSIX-compliant computer operating system released by Apple Inc. in 2000."