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”