| Operating system | Developer | First release | License |
|---|---|---|---|
| CP/M | Digital Research, Gary Kildall | — | BSD licenses |
| Fuzix OS | Alan Cox | — | GNU General Public License, version 2.0 |
| MP/M | Digital Research, Tom Rolander | — | proprietary license |
| OASIS operating system | — | — | — |
| TurboDOS | — | — | — |
| UCSD p-System | — | — | — |