CP/Mish is an open source sort-of-CP/M distribution for the 8080 and Z80 architectures (although for technical reasons currently it only works on the Z80).
It contains no actual Digital Research code. Instead, it’s a collection of third party modules which replicate it, all with proper open source licenses, integrated with a build system that should make it easy to work with.[…]
CP/Mish is not CP/M, but it’s enough like CP/M to run CP/M programs and do CP/M things. And, if you want the real CP/M, CP/Mish uses the standard interaces so you can just drop in a Digital Research BDOS and CCP and it’ll work.
Some companies bet on CP/M, some bet on DOS. We know who won, and who lost. Still, CP/M inspired a lot of DOS, so anybody with experience with DOS should feel right at home on CP/M.