Three ideas for "license-free settings".
1. Fantasy Swashbuckling
I still want to play in a pseudo-late 16th century / early 17th century (1660-1710? Ish?) setting. Musketeers, Pirates of the Caribbean, Voyages of Discovery, Nippon, Cathay, Wars of Religion, black powder and melee weapons, plus of course lots of lovely baroque magic. You could centre it where you liked for the core book - say, Restoration England, the Sun King's court, or German(ia) in the Thirty Years' War, then produce all manner of "license-free" setting books for:
The Three Musketeers
Pirates of the Caribbean
Shogun
Master and Commander
The Great Embassy to China
Robinson Crusoe
Inca and Aztecs
Salem Witch Trials
Alchemists
Pre-Petrine Russia
The Ottoman Empire
Siege of Vienna
Sort of, say, the Fantasy Europe of RQ3, but a thousand years later, and doing the whole world!
2. Pulp Sword & Planet
Second, Jason's Interplanetary is a killer setting which could spawn all kinds of settings books a la John Carter and Flash Gordon, but again without requiring a license. I think the scope for beautifully crafted worlds and "sub-settings" here could really let you go to town. "Witch-Queen of Venus" and "Nightmare Men of Jupiter" here we come!
3. Foundation / Space Opera
This is "the scifi trope everybody knows". There's this huge galactic empire, run by humans but with gazillions of alien races, sufficiently large that there is no "one true world" viewpoint. There are spinoff civilizations, wars, explorations, lost worlds, the whole shebang. You just write a world (or a few) and plug it in. Stick it a few thousand years in the future, and you can have your Star Wars, Galacticas, Buck Rogers, and Star Treks all rubbing shoulders with minimum hassle.
Cheers!
Sarah