Maxperson
Morkus from Orkus
These all seem to be based on the assumption that the player is still playing in the game. If a player is in the game and a former PC from another campaign is encountered, I leave it to the player of that PC to roleplay what the character does. He knows the character best.So, the details matter.
When a player sits down at the table to play their character, there is an at least implicit agreement about what kind of stuff will happen - possibly an explicit agreement, if you run a solid Session Zero.
Beyond that - the tables I've run at for the past 15+ years have had separate agreements about what might happen if the player isn't at the table - including how much risk the character will be in if their character is present, but run by the GM or another player.
I think there ought to be yet another agreement if the character is going to be used as an NPC in a context beyond the campaign the PC was being played in.
I'm talking about what happens when a player leaves the game entirely. There is no obligation for me to track down the player and ask permission to roleplay the now NPC in my game.
That said, I do agree that session zero clarifications are a good thing and do run a session 0 in my games.
Unlike most intellectual property, a character is made to be shared in the game world. Primary control resides with the player, but there are times when the DM can and does take over for a bit. The character(s) and the game as a whole belong to everyone playing in the collaborative effort.Broadly - the PC is the player's intellectual property. Make an agreement on how you use it when it is borrowed.
I've yet to be in a social contract that assumes that if a player leaves the game entirely, the DM can't use the character as an NPC.Yeah, but "there is no legal harm" is not the basis of the social contracts we work under.