Is there any EU content explaining how planet ownership works? I guess that alien races own their homeworlds, but, what about planets without sentient life? I know corporations own planets, but, how does it work? Do they buy them from the Republic? from the sectorial governments? If you arrive to an unexplored, unclaimed system in Wild Space or the Outer Rim, can you claim a planet?
Yes, but Pantora was the moon of Orto Plutonia. The ancient human/Zhell settlers of Pantora probably claimed Orto Plutonia long ago. If a mining company wants to own Yavin, for example, what do they do? Do they have to pay a sum to the Senate? And if you discover an unexplored and uncharted system, which are the requirements to claim a planet? I don't think somebody like Han Solo can land on, say Dagobah and claim it as his own. There must be some previous condition in order to claim a new world, like setting a colony, or investing a certain amount in building infraestructures, or paying a fee to the Republic.
Probably depends on the era. From Specter of the Past: "This whole place makes me nervous," Elkin growled, drumming his fingertips restlessly on the edge of his control panel. "Why isn’t there anything on either the planet or system in the datafiles? It’s got a name - someone must have been here once," "Oh, someone was here, all right," Faughn agreed. "But probably not for very long. For a while back in the Old Republic you could basically just come into an unknown system, do a quick life-forms scan, and file for development rights - the "name it, claim it" law, they called it. You had systems all over the Outer Rim put on maps and asset lists without anyone having the slightest idea what was actually there." "I remember reading about that," Mara said. "The Corporate Sector was especially bad about abusing the privilege, and we’re not all that far from there."
Specter was written a little before TPM - but I could see the "for a while" period as actually being the PT era rather than decades or centuries before.
In "The Courtship Of Princess Leia", Han manages to win ownership of Dathomir which is an inhabited world, during a game of Sabacc.
I have found a mention in the Unknown Regions sourcebook that Czerka Mining corporation found an inhabitable world in the Unknown regions, Volik, claimed it and sold it to Vekanda Leisure Colonies. Dathomir was in Drackmarian space, which wasn't part of the Republic (and while the Empire defeated the Drackmarians, they never formally became part of the Empire).
I have discovered the answer in the Galaxy Guide: Scouts sourcebook. Anybody who discovers a new planet, moon or asteroid can register it, but, if it's inhabitable, he or she must "improve and develope" the planet before a set period of time or they lose ownership. If the planet, moon or asteroid isn't inhabitable, they can keep it for themselves.
Jedi Quest #6 is set on a planet with no government and no owner but several groups living there. It is called an "Open Planet", which sounds like an official classification but I haven't seen the term anywhere else (not rare for Watson books).
In the Black Fleet Crisis books, Atzerri is a "Free Trader planet" and is pretty lacking in regulations. "Free Traders are the closet anarchists of the galaxy" as Luke puts it.