| Nura | — | — | GNU General Public License, version 3.0 |
| Omarchy | David Heinemeier Hansson | — | MIT License |
| OpenBSD | OpenBSD Project, Theo de Raadt | — | ISC license |
| OpenIndiana | — | — | — |
| OpenMandriva | — | — | GNU General Public License |
| OpenMediaVault | Volker Theile | 2009 | GNU General Public License, version 3.0 |
| OpenSUSE | OpenSUSE Project | — | GNU General Public License |
| OpenVMS | VMS Software Inc., Hewlett-Packard, Digital Equipment Corporation, Compaq | 1977 | proprietary license |
| OpenWrt | Gábor Juhos, Florian Fainelli, Hauke Mehrtens, Jo-Philipp Wich | 2004 | GNU General Public License, version 2.0 |
| OPNsense | — | — | 2-clause BSD License |
| Oracle Linux | Oracle Corporation | 2006 | GNU General Public License |
| OS X El Capitan | Apple Inc. | 2015 | Apple Public Source License |
| OS X Mavericks | Apple Inc. | 2013 | Apple Public Source License |
| OS X Mountain Lion | Apple Inc. | 2012 | Apple Public Source License |
| OS X Yosemite | Apple Inc. | 2014 | Apple Public Source License |
| Parabola GNU/Linux-libre | — | — | GNU General Public License |
| Parch Linux | — | — | GNU General Public License |
| PfSense | — | — | Apache License |
| Plan 9 | Bell Labs | 1992 | GNU General Public License, version 2.0, MIT License, Lucent Public License |
| Pop!_OS | System76 | 2017 | GNU General Public License |
| Porteus | — | — | GNU General Public License |
| PureOS | Purism | — | Creative Commons Attribution-ShareAlike 4.0 International |
| Q4OS | — | 2013 | GNU General Public License |
| Qubes OS | — | — | GNU General Public License, version 2.0 |
| ReactOS | Amine Khaldi, Timo Kreuzer, Eric Kohl, Hermès Bélusca-Maïto, Cameron Gutman | — | GNU Lesser General Public License, GNU General Public License |
| Red Hat Enterprise Linux | Red Hat | 2002 | — |
| RED OS | — | — | commercial software |
| Red Star OS | Korea Computer Center | — | — |
| Redox | Jeremy Soller | — | MIT License |
| Rocks Cluster Distribution | San Diego, University of California, San Diego Supercomputer Center | — | — |
| Rocky Linux | Rocky Enterprise Software Foundation | — | 3-clause BSD License |
| ROSA Linux | LLC "STC IT ROSA" | 2011 | GNU General Public License, version 2.0 |
| RTEMS | Sebastian Huber, Joel Sherrill | — | GNU General Public License |
| Runtu | — | — | — |
| Sabayon Linux | — | — | GNU General Public License |
| ShredOS | — | — | GNU General Public License, version 2.0 |
| Siduction | — | 2011 | GNU General Public License |
| Slackware | Patrick Volkerding | — | GNU General Public License |
| SmartOS | Joyent | — | Common Development and Distribution License version 1.0 |
| Solaris | Sun Microsystems, Oracle Corporation | 1991 | proprietary license |
| SparkyLinux | — | — | GNU General Public License |
| SteamOS | Valve Corporation | — | — |
| Tails | The Tor Project, Inc | 2009 | GNU General Public License v3.0 or later |
| TempleOS | Terry A. Davis | 2013 | — |
| Tizen | Intel, Linux Foundation, Samsung Group, Tizen Association | — | Apache Software License 2.0, Flora License |
| Trisquel | — | 2007 | GNU General Public License, version 3.0 |
| TrueOS | IXsystems, Kris Moore | 2006 | BSD licenses |
| Ubuntu | Canonical Ltd. | 2004 | — |