OpenBSD is an operating system descended from Berkeley Software Distribution (BSD), a Unix derivative developed at the University of California, Berkeley. It was forked from NetBSD by project leader Theo de Raadt in late 1995. The project is widely known for the developers' insistence on open source code and quality documentation, uncompromising position on software licensing, and focus on security and code correctness.
OpenBSD includes a number of security features absent or optional in other operating systems, and has a tradition in which developers audit the source code for software bugs and security problems. The project maintains strict policies on licensing and prefers the open-source BSD licence and its variants: in the past this has led to a comprehensive licence audit and moves to remove or replace code under licences found less acceptable.
In October 1995, de Raadt founded OpenBSD, a new project forked from NetBSD 1.0. The initial release, OpenBSD 1.2, was made in July 1996, followed in October of the same year by OpenBSD 2.0. Since then, the project has followed a schedule of a release every six months, each of which is maintained and supported for one year. The latest release, OpenBSD 4.6, appeared on October 18, 2009.
This verison of OpenBSD, 4.6, was downloaded from ftp.openbsd.org/.