Lucas actually openly admits that he borrowed it from Kurosawa. and Kurosawa wasn't immune to committing homage either. He borrowed from the westerns and from shakespeare for his sources.
There are no uninfluenced filmmakers ever... even the lumiere bros were influenced by photography, and edison by carnivals, burlesque and stage performances. Truffaut frequently made films from literature and Almodovar borrowed HEAVILY from hitchcock.
Infact, pixar continues the traditions:
Nemo = Pinocchio
Bug's Life = Magnificent 7 = 7 Samurai
Incredibles = Watchmen
Cars = Doc Hollywood
I love the reinterpretations that all of these filmmakers present of loved films... their homage reinvigorates interest in the originals. Like Tom's Diner from Suzanne Vega and that horrible sampled remake of the song, she didn't sue them for remixing her song because she had an album coming out and it helped promote her
Moreover, check out IMDB for "the prisoner of zenda" and "robin hood"
and
Aeon Flux = Zardoz
The Island = Logan's Run
I'm sure the list goes on, I find it fascinating and it makes for great film studies papers