z/VM, z/Linux (bare metal or under VM), z/VSE, z/OS, and I believe z/TPF. That's the newest stuff. It will also emulate 360's. I think the first thing I ever ran on Hercules was OS/360 MFT! Anyone can legally run VM/370 and MVS 3.8(?) and anything older. Oh ya, MTS, Music/SP, etc. too.