[jeremygaither]

macOS runs the Darwin kernel (developed at NeXT using the Mach kernel, then at Apple). NeXTSTEP was based on a BSD UNIX fork. Development of BSD at Berkeley started in 1977. NeXT worked on their kernel and the BSD UNIX fork in the '80s and '90s before being purchased by Apple. NeXTSTEP formed the base of Mac OSX (which is why much of the Objective-C base libraries start with `NS-something`. There is 45 years worth of development on UNIX, and Linux is a completely different kernel with a completely different license. Linux kernel has been in development for about 31 years.

Languages and understanding them is not special, but decades of development of two different kernels is a huge time investment. Even though Linus Torvalds wrote the basic Linux kernel in 5 months, it was very simple at first.

I doubt writing an entire POSIX-compatible replacement for a kernel would be a small or quick endeavor, and Apple has shown resistance to adopting anything with a GPL 3 license iirc. That is why they switched to ZSH from Bash.

[Dylan16807]

The earlier post seemed more focused on the userland, so we should very much consider excluding the kernel before we decide the idea is too hard.