What would be the motivation for Apple to do such a thing? MacOS is already a Unix, with a BSD-based userland. Also, they are doing active kernel development -

What would be the motivation for Apple to do such a thing? MacOS is already a Unix, with a BSD-based userland. Also, they are doing active kernel development - as in architecture development - to enhance the system security, so that even root cannot compromise the system. One part of this is moving kernel extensions into user processes thanks to the fact that Mach is a microkernel. They couldn't do that with the current Linux architecture.