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 5 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.