Your best bet is probably the old MVS that was open sourced back in the 70s or 80s and lives on via an emulator called Hercules. Its sufficiently different to be worth a look, it's got a living direct descendent…
Your best bet is probably the old MVS that was open sourced back in the 70s or 80s and lives on via an emulator called Hercules. Its sufficiently different to be worth a look, it's got a living direct descendent…