Plan 9

In the late 1980s, researchers at Bell Labs (especially Rob Pike of Kernighan & Pike fame) got bored with the limitations of UNIX and decided to reimplement the entire system. The result was called Plan 9 in “the Bell Labs tradition of selecting names that make marketeers wince.” The developers also wished to pay homage to the famous film, “Plan 9 From Outer Space”, considered by some to be the worst movie ever made. The source is available for download under open-source terms. The developers and a small fan base hang out at comp.os.plan9, where one can occasionally hear “If you want UNIX, you know where to find it”