| 9front | — | — | MIT License |
| Amoeba | Andrew S. Tanenbaum | — | MIT License |
| CubiOS | CubiOS Inc. | — | — |
| Harvey OS | — | — | GNU General Public License, version 2.0, Lucent Public License |
| Inferno | Vita Nuova Holdings, Bell Labs | — | GNU Lesser General Public License, MIT License, GNU General Public License |
| Jehanne | — | — | GNU General Public License, version 2.0, GNU Affero General Public License, version 3.0, MIT License |
| LegoOS | — | — | GNU General Public License, version 2.0 |
| Octopus | — | — | — |
| OpenHarmony | Huawei, OpenAtom Foundation | 2020 | Apache Software License 2.0 |
| OpenVMS | VMS Software Inc., Hewlett-Packard, Digital Equipment Corporation, Compaq | 1977 | proprietary license |
| Plan 9 | Bell Labs | 1992 | GNU General Public License, version 2.0, MIT License, Lucent Public License |
| Plan B | King Juan Carlos University | — | — |
| Sprite | University of California, Berkeley | — | MIT License |