BSD

BSD stands for Berkeley Software Distribution and is a fork from AT&T's 6th edition Unix. The first version of BSD, 1BSD appeared in 1976. Since 4BSD it was developed by the CSRG at the University of California at Berkeley (UCB).

A few projects evolved out of the latest version of BSD which was 4.4BSD lite and they are called FreeBSD, NetBSD, OpenBSD and DragonflyBSD.