Berkeley Software Distribution

Darwin is an open-source Unix operating system released by Apple Inc.

IPFilter (commonly referred to as ipf) is an open-source software package that provides firewall services and network address translation (NAT) for many Unix-like operating systems.

Ultrix (officially all-caps ULTRIX) is the brand name of Digital Equipment Corporation's (DEC) discontinued native Unix operating systems.

OpenServer, previously SCO UNIX and SCO Open Desktop (SCO ODT), is a closed source computer operating system developed by Santa Cruz Operation (SCO), later acquired by SCO Group, and now owned by Xinuos.

BSD licenses are a family of permissive free software licenses, imposing minimal restrictions on the redistribution of covered software.

DYNIX (dynamic unix) is a discontinued operating system developed by Sequent Computer Systems.

386BSD, sometimes called "Jolix", was a free Unix-like operating system based on BSD, first released in 1992.

DEMOS (meaning "Dialogovaya Edinaya Mobilnaya Operatsionnaya Sistema" (Диалоговая Единая Мобильная Операционная Система, ДЕМОС), or "Interactive Unified Portable Operating System") was a Unix-like operating system developed in the Soviet Union.

OpenStep is an object-oriented application programming interface (API) specification for a legacy object-oriented operating system, with the basic goal of offering a NeXTSTEP-like environment on a non-NeXTSTEP operating system.

SunOS is a Unix-branded operating system developed by Sun Microsystems for their workstation and server computer systems.

MirOS BSD (originally called MirBSD) is a free and open source operating system which started as a fork of OpenBSD 3.

RISC iX is a discontinued Unix operating system designed to run on the Acorn Archimedes.

ULE is the default scheduler for the FreeBSD operating system (versions 7.1 and forward) for the i386 and AMD64 architectures.

NeXTSTEP is a discontinued object-oriented, multitasking operating system based on UNIX.

BSD/OS (originally called BSD/386 and sometimes known as BSDi) was a proprietary version of the BSD operating system developed by Berkeley Software Design, Inc.

Berkeley Software Distribution (BSD) is a Unix operating system derivative developed and distributed by the Computer Systems Research Group (CSRG) of the University of California, Berkeley, from 1977 to 1995.

PacBSD (formerly known as Arch BSD) is an operating system based on Arch Linux, but uses the FreeBSD kernel instead of the Linux kernel and the FreeBSD userland instead of the GNU userland.

iXsystems, Inc. is a privately owned American computer technology company based in San Jose, California that develops, sells and supports computing and storage products and services.

Gentoo/Alt is a Gentoo Linux project created to manage porting the Portage framework and other features to other operating systems, such as Mac OS X and the free BSDs.

Berkeley Software Design Inc.

Rhapsody was the code name given to Apple Computer's next-generation operating system during the period of its development between Apple's purchase of NeXT in late 1996 and the announcement of Mac OS X in 1998.

NextBSD is an operating system initially based on the trunk version of FreeBSD as of August 2015.

MachTen is a Unix-like operating system from Tenon Intersystems.

Nagare is a free and open-source web framework for developing web applications in Stackless Python.

MacMach is a computer operating system from the early 1990s, developed by Carnegie Mellon University.

Academic Operating System (AOS) was IBM's version of 4.