The Unix operating system has so many descendants and variations that organizations navigating the maze of choices can quickly become disoriented. Many of these projects were launched to offer operating systems unencumbered by the commercial and proprietary licenses tied to the original AT&T UNIX. One of the first open source major branches to develop this way is the BSD family, which has since spawned a number of descendants, including FreeBSD, NetBSD, and OpenBSD. Apple's Mac OS X is also based on a BSD operating system known as Darwin.
People often use the term "family" to describe the lineage of Unix operating systems, and the word is an apt metaphor. Think of each operating system as being a distinct personality -- the erudite grandfather, the know-it-all cousin, the doting mother. Like a family, they have many traits and capabilities in common and also differ in their strengths and weaknesses. Therefore, when trying to decide on an operating system, bear in mind that it is not so much a case that one Unix operating system is "better" than another, but which is the best choice for a given environment. Would you rather take your cousin to the movies, or your grandfather to a nightclub?
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