Oh, yeah, that's a famous bug in FC8. gnuplot doesn't actually depend on all that stuff and they've fixed it since. FC8's end-of-lifed though so it's not gonna benefit. (Olivier bitches them out regularly when they do stuff that makes his large lab suck).
Also, I'm the guy who defends Vista on MAMEWorld, home of the Win98 holdout ;-)
ETA: you might try just getting the RPM itself and installing it with --nodeps.