Ну вот с такими глупостями лучше бы молчать

This is as much a myth about OS X as about FreeBSD: that OS X is just FreeBSD with a pretty GUI. The two operating systems do share a lot of code, for example most userland utilities and the C library on OS X are derived from FreeBSD versions. Some of this code flow works in the other direction, for example FreeBSD 9.1 and later include a C++ stack and compiler that were originally developed for OS X, with major parts of the work done by Apple employees. Other parts are very different.

The XNU kernel used on OS X includes a few subsystems from (older versions of) FreeBSD, but is mostly an independent implementation. The similarities in the userland, however, make it much easier to port OS X code to FreeBSD than any other system. For example, both libdispatch (Grand Central Dispatch in Apple's marketing) and libc++ were written for OS X and worked on FreeBSD before any other OS.