*BSD Unix

BSD Unix is little known to the general business community, but widely used among ISPs (Internet Service Providers) and software developers. There are several versions of BSD Unix, each by a different development group, each emphasizing particular characteristics. Several BSD varieties are free and open source. Most BSD versions can now run software from other Unix varieties and derivatives, particularly Linux.

All BSD varieties have their roots in the version of Unix developed by the Computer Systems Research Group at the University of California at Berkeley.

• FreeBSD - open source - Emphasis is high performance and stability, especially in an Internet context. Many Internet Web servers run FreeBSD. FreeBSD is said to run Linux applications faster than Linux does. The FreeBSD license allows incorporation of it's code into commercial products.
• OpenBSD - open source - Emphasis is security. Not only is OpenBSD highly secure, but a number of commercial security products are based on it. Open BSD can run programs written for a number of other operating systems, including SVR4 (Solaris), FreeBSD, Linux, BSD/OS, SunOS and HP-UX.
• NetBSD - open source - Emphasis availablility on a great many computing platforms. They've got a list on the right sidebar of their Web page.
• BSD/OS - Commercial - A BSD for those who wnat a Unix product supported by a specific company that offers service contracts. BSD/OS is most used for Internet servers.
• Darwin - open source - The version of BSD that is the foundation of Apple's new OS X oprating system. It is derived from elements of FreeBSD, OpenBSD, NetBSD and the Mach kernel from the Carnegie-Mellon University.

Further information can be found at BSD.org.