A pseudo
free implementation of an
X11 server, as implemented by the
X consortium for
386-class PCs. It never
kept up with features and was
buggy and
slow as all get-out, and a couple of people wanted to fix all its problems and improve it but the X consortium decided to be
bastards and not accept
outside patches.
And so XFree86 was born (its name is a pun on X386, and never really had anything to do with the architecture it ran on). Originally it was based heavily on the X386 code, but it's been completely rewritten from scratch as of XFree 4.0.