BSD

The BSD (an acronym for 'Berkeley Software Distribution') systems are a family of Unix operating systems that were developed at the University of California, Berkeley during the 70s, 80s, and 90s, building atop the UNIX v6 and UNIX 32/V releases from Bell Labs.

As a result of their permissive open-source licensing, the BSDs frequently see their work incorporated in other systems. For example, Microsoft's Windows OS has a TCP/IP stack derived from BSD.

There are 6 main BSD operating systems in use today; these are FreeBSD, a general purpose OS; OpenBSD, an OS acclaimed for its security principles and notable head, Theo de Rats; NetBSD, which is a BSD designed for running in household appliances such as toasters; OS X, a proprietary desktop from Apple; and Dragonfly BSD, a derivative of an older release of FreeBSD that introduces a new multiprocessing paradigm, while being suitable for desktop use and attempting to revive the spirit of AmigaOS for the 21st century. PCBSD, which is made for simplicity and ease of use and is a direct derivative of FreeBSD.