M/PC – A Concatenative OS

Does this name come from reversing "CP/M"?

maybe I am dumb, but I don't really get how this is different to just piping between commands?

Not to be confused with MPC, apparently: https://en.wikipedia.org/wiki/Multimedia_PC

Is this not more of a shell than an os?

Nevertheless an interesting idea. Unix pipes are basically concatenative, I've often thought how much mileage you could get out of going more in this direction.

Having said that. This has a lot of forth in it. (Dup, over, rot) I'm not sure the forth way, of passing options in the stack would necessarily work so well in a shell.