Alidar Jarok wrote:
Why would Marvel Studios have to be developing a character to preserve it? Aren't they the ones who own it by default?
That's right. It's the other studios, the ones who acquire licenses to the characters, who eventually lose those licenses if they don't use them. That's to keep other studios from acquiring a property and sitting on it just to keep the rightful owner from using it. Unless they actually use the character or concept, eventually the rights revert to the owner.
Now, trademarks tends to lapse if they aren't actively used. That's how Fawcett's trademark on the name "Captain Marvel" lapsed, allowing Marvel to snatch it up for a new character. But that's different from losing the rights to the actual character, as opposed to just the name. DC needed to acquire a license in order to use the original Captain Marvel/Billy Batson character. Names, titles, and logos are trademarked, while characters and concepts are copyrighted.
So if, say, Marvel went a couple of decades without using the Sub-Mariner, the trademark on the name could lapse and another company could theoretically create their own character named Sub-Mariner. But it wouldn't be Prince Namor, the mutant king of Atlantis. Only the name would become public domain.