| Source Mage | — | — | — |
| Splashtop OS | Splashtop Inc. | — | — |
| SuSE Linux | SUSE, Novell | — | GNU General Public License |
| SUSE Linux Enterprise Desktop | SUSE | — | GNU Lesser General Public License |
| Syllable Desktop | — | — | GNU General Public License |
| Symbian | Symbian Foundation, Nokia, Symbian Software | — | proprietary license |
| Tiny Core Linux | — | — | GNU General Public License |
| Tizen | Intel, Linux Foundation, Samsung Group, Tizen Association | — | Apache Software License 2.0, Flora License |
| Ubuntu | Canonical Ltd. | 2004 | — |
| Ubuntu for Android | Canonical Ltd. | — | GNU General Public License |
| Ubuntu GNOME | Canonical Ltd. | 2016 | GNU General Public License |
| Ubuntu Server Edition | Canonical Ltd. | 2006 | GNU General Public License |
| Ubuntu Touch | UBports | 2013 | GNU General Public License |
| UCS@school | Univention | — | GNU Affero General Public License |
| UCSD p-System | — | — | — |
| UnixWare | Novell, SCO Group, Caldera, Santa Cruz Operation, Univel | — | proprietary license |
| VectorLinux | — | — | — |
| Visopsys | — | — | GNU General Public License, version 2.0 |
| Vitalinux | — | — | — |
| VxWorks | Wind River Systems | — | end-user license agreement |
| Wear OS | Google | 2014 | Apache License |
| Webconverger | — | — | — |
| Whonix | — | 2012 | GNU General Public License |
| Windows 2.0 | Microsoft | 1987 | proprietary license |
| Windows 2.1 | Microsoft | — | proprietary license |
| Windows 2000 | Microsoft | 2000 | proprietary license |
| Windows 7 | Microsoft | 2009 | volume licensing, Microsoft Software Assurance, end-user license agreement |
| Windows 8 | Microsoft | 2012 | end-user license agreement |
| Windows 8.1 | Microsoft | — | end-user license agreement |
| Windows 95 | Microsoft | — | proprietary license |
| Windows 97 | Microsoft | — | — |
| Windows 9x | Microsoft | — | — |
| Windows Embedded Compact | Microsoft | — | end-user license agreement |
| Windows Me | Microsoft | 2000 | Microsoft end-user license agreement |
| Windows Nashville | Microsoft | — | — |
| Windows NT 3.5 | Microsoft | — | commercial software, proprietary license |
| Windows NT 3.51 | Microsoft | 1995 | proprietary license |
| Windows Server 2000 | Microsoft | 2000 | — |
| Windows XP Embedded | — | — | Microsoft end-user license agreement |
| Windows XP Tablet PC Edition | Microsoft | — | — |
| Woof | — | — | — |
| Xenix | Microsoft, Santa Cruz Operation, AT&T Corporation | — | proprietary license |
| XTS-400 | BAE Systems | — | — |
| Xubuntu | Canonical Ltd., Ubuntu Foundation | 2006 | — |
| Yanux | Luch Scientific Production Association | — | — |
| YunoHost | — | — | GNU Affero General Public License, version 3.0 |
| Zenwalk | — | — | GNU General Public License |
| Zephyr | Wind River Systems, Linux Foundation | — | Apache Software License 2.0 |