| Jarro Negro | — | — | — |
| Java Card OpenPlatform | IBM | — | — |
| JavaOS | Sun Microsystems | — | proprietary license |
| Jazz Linux | — | — | — |
| Jehanne | — | — | GNU General Public License, version 2.0, GNU Affero General Public License, version 3.0, MIT License |
| JeOS | Canonical Ltd. | — | GNU General Public License |
| JesusFreke ROM | — | — | GNU General Public License, version 2.0 |
| JetOS | Institute for System Programming, State Research Institute of Aviation Systems | — | — |
| Jibbed | — | — | BSD licenses |
| Jlime | — | — | GNU General Public License |
| JNode | — | — | GNU Lesser General Public License |
| Joatha Linux | — | — | — |
| Joli OS | — | 2011 | GNU General Public License |
| Jolicloud | — | — | proprietary license |
| Junos | Juniper Networks | — | — |
| Jurix | — | — | GNU General Public License |
| JUX | — | — | — |
| JX | University of Erlangen–Nuremberg | — | GNU General Public License |