He's also very generous about letting people write deriivations of the Star Wars saga without having to pay royalties. He is zealous about guarding the SW trademarks, but is amazingly generous about the copyright.
Here's a fun one for you: have you ever noticed at Tatooine Traders that while there are lots of various costumes and helmets around, you never see an adult Storm Trooper mask? It is the one item of SW costuming that Lucas refuses to license. The only way to get one is to make it yourself or buy it from someone who has done it by hand. Owning such Stormtrooper armor is an entrance requirement for membership in the 501st Legion (the costume club that appears at the Studios during SWW, and which marched in the Rose Bowl Parade when Lucas was Grand Marshall.) They don't pay Lucas for the right to use the likenesses, but they have agreed not to reproduce them commercially. Most of the members make their own.
(And no, I'm not a SW geek. My 13 yo Aspie son is. Whenever he has to do a report on a "great American", DS always chooses Lucas because of his business savvy. We noticed the trademark statement on the Droid phone the first day that it came out -- it is on the phone's packaging, too.)