Look kids. Get over the small minded philosophical hangups. Understand that the MacBook OS is a BSD kernel + the GNU OS (tool chain) + Plus the NSstuff that Next brought. That's it. The vast majority of code is already open, because it has been developed by the community over 30 years.
the XNU kernel is an evolved version of the XNU kernel from NextSTEP that uses some BSD components, CMU Mach microkernel components and C++ I/O Kit which replaced NextSTEP's ObjC DriverKit. It's not a "BSD kernel" per say. the toolchain is definitely not GNU at all. LibSystem uses no GNU code at all. It uses the BSD standard library libc, not glibc. clang is the compiler, not gcc as that's something they got rid of many years ago. They do still use some software preinstalled that are under GPL but it's no "toolchain". See Apple’s great GPL purge.
A number of important components are completely closed which are needed to boot XNU on its own, like PlatformExpert. So you're not exactly correct in your statement here.