So, is it your position that a group of players can't fire a GM and have someone else run his world either? Such things can and do happen, admittedly with less frequency. I'm sorry but the people playing the game define the game. Period. There are no values external to the gaming table in operation here.
1) I have NEVER heard of such a situation.
2) Players can QUIT a campaign and even refuse to ever play in a particular person's campaigns, but if someone tried to "fire me" and run MY campaign that I put countless hours into designing, that new guy would have a devil of a time getting my campaign notes, maps, NPC/Homebrew monster stats, etc. That GM would also not be welcome in my house.
(And thats BEFORE I'd even contemplate paying $30 for formal copyright protection by filing with the Library of Congress- I'm not trying to make this ugly, but I could if I wanted.)
3) Just because external values haven't been enforced doesn't mean they CAN'T be.
Let me be PERFECTLY clear- I'm in a couple of campaigns, one of which has been active since 1986 or so. That one has 3 DMs who work in a round robin fashion- each has multiple characters (of various levels) in the campaign as well. Those PCs are treated as NPCs when the need arises- but ABSOLUTELY no SUBSTANTIVE changes are made to those characters unless they are made by the player who created them.
People change things in Tolkien's world all the time...it is in the nature of RPGs to do this
Yes, that's true. AND its unlikely that any writer would ever sue a gaming group for doing so...until/unless they tried to sell product based on their changes.
The question that started this was "who do the characters belong to." The law is pretty clear that they belong to their creators...as does the campaign to its creator.
Relationships in a game group should never rise to the level of a lawsuit about ownership rights over IP. The BEST way to avoid this is to minimize the amount of interference with other people's PCs.
Simply put- you DON'T mess with someone else's creations without permission, these issues don't arise.
For example: Marvel and DC Comics (and other comic book companies) get around this ALL the time by use of a simple device- CHANGE THE NAMES and DETAILS.
Marvel's Squadron Supreme was CLEARLY based on DC's Justice League. Legal action was threatened, but ultimately, despite similarities, Marvel changed the characters enough to give them a distinct identity apart from their origins.
Similarly, when DC killed Superman off in the Doomsday story arc, every comic company that did superheroes launched their own version of the Superman character- each a different enough take on the icon that they were new and yet identifiable as a variation on the theme.
So if I wanted to use one of my players' characters as an NPC, I would use it only as a starting point- I'd change the name and certain details- I'd remake the character into something different.