A free version of UNIX that is based on the BSD 4.4 operating system and is maintained and supported by a large community of developers.
The OpenBSD project is headed by Theo de Raadt, a computer science graduate of the University of Calgary in Alberta, Canada. OpenBSD is widely viewed as one of the most secure UNIX platforms available; even its default installation is fairly hacker-proof. OpenBSD includes support for the Kerberos IV security protocol and Internet Protocol Security (IPSec).
OpenBSD also supports binary emulation of most software written for other popular UNIX flavors, such as HP-UX, SunOS, Solaris (SVR4), Linux, and FreeBSD. The current release of the OpenBSD software is version 2.5.