Gary Kurtz, who was as much of a creative force in the first two Star Wars films as Lucas (some say he was far more active in Empire than Lucas) can't stand Lucas' meddling. He's one of many important individuals unhappy with the changes ... individuals whose work was evident in the first three films. Lucas has crapped on hundreds of artists' contributions.
Yeah, Lucas created the characters. And yes, he owns the copyright. That's unfortunate and it's the reason why studios usually acquire full rights to properties ... so the creators can't go in later and devalue the property.
Lucas has gone batshit crazy ... too bad he only has Yes-men and no real friends to help him out.