Not just userspace - OSX adopted large pieces of FreeBSD kernel, including the syscall layer and the network stack. Also, Mach isn't technically a microkernel

Not just userspace - OSX adopted large pieces of FreeBSD kernel, including the syscall layer and the network stack. Also, Mach isn't technically a microkernel - the whole kernel runs in Ring 0. But yeah, OSX kernel is vastly different from FreeBSD - first, there were huge differences to start with, only some pieces of kernel were adopted, and finally there were thousands of man-hours put into each system afterwards, diverging them even more.