I think it all kind of gets sketchy. Because personally, if I wrote something and created characters for that something, they would be MY creations, not anyone elses. Certainly the producers, actors, and many other people involved making whatever I had written into something on screen would be responsible for bringing those characters TO LIFE, nothing more.
In a lot of interviews surrounding the new Buffy Season 8 comics, Joss Whedon is asked if he'll cross over Angel and Spike to the S8 comics, as they were both on Angel the Series when it went off the air. And he always says that while HE OWNS the characters and can do WHATEVER HE WANTS with them, though he chooses not to because he likes what IDW, the publishers behind the current Angel comics, is doing with the characters, and he doesn't want to step on their toes.
Isn't that normal? I mean, I would think it is, because FOX produced Buffy the television show, and if you want to get something licensed with the Buffy name on it, you have to go through FOX and Joss, but generally if Joss approves it, FOX says nothing of it.
I guess it just comes down to small details.