The original DUNE movie had alot of trouble bringing the book to the screen, because STAR WARS took so many ideas from it ...
The original Dune movie crashed and burned long before Star Wars because studios weren't interested
. The subsequent Lynch-directed Dune, like so many other subsequent space adventures (BSG, for example) gets made because
of Star Wars.
Besides, one could also say Lucas ripped off Asimov's Foundation
and Kurosawa's Hidden Fortress
, as well as Buck Rogers
and half-a-dozen other influences. The fact is, Lucas' creation is a truly unique amalgamation of pre-70s pop culture and classic mythic archetypes.