Why is Mac OS X/iOS not called a flavor of Unix? Because for a time, Unix was a trademark, therefore everybody else didn't have a unix offereing, but a Solaris

Why is Mac OS X/iOS not called a flavor of Unix? Because for a time, Unix was a trademark, therefore everybody else didn't have a unix offereing, but a Solaris, a A/UX, a A/IX, a Xenix, a FreeBSD, an OpenBSD, a Darwin, a GNU/Hurd, a GNU/Linux, etc. OSX and iOS are built on linux No. They're built on Darwin/Mach. Why aren't they called flavor of linux? Because they have not a single bit in common with Linux.