https://en.wikipedia.org/wiki/MkLinux - linux on top of the mach microkernel, I think it was sponsored by Apple (especially its book was great)
https://en.wikipedia.org/wiki/L4Linux
[1] http://www.puredarwin.org/
[2] https://github.com/PureDarwin/PureDarwin
https://en.wikipedia.org/wiki/MkLinux - linux on top of the mach microkernel, I think it was sponsored by Apple (especially its book was great)
https://en.wikipedia.org/wiki/L4Linux