Board Thread:General Discussion/@comment-4548390-20160910091011/@comment-61022-20160912194520

From what I can tell, and this is by no means any official stance, but it looks like Fox has rights over assorted characters who first appeared in the first fifty issues of Fantastic Four.

There are a few characters who fall into this category: Naturally anyone who guest starred in a given story or was first introduced somewhere else (IE: the Sub-Mariner, Sandman, the X-Men, Spider-Man etc) The only characters in this 50 year run that don't appear to be included are the Inhumans -- at least as a race. Who knows what the licensing is for Medusa (since she was introduced before being called an Inhuman), or the rest of the royal family.

The reason why this makes sense is that Fox clearly has the rights to the Silver Surfer and Galactus, given they were in Rise of the Silver Surfer. However you take a look at characters who appear in the MCU that first appeared in Fantastic Four, namely the Black Panther (FF #52), the Kree (FF #64) Ronan (FF #65), and Adam Warlock (#66/67) all appear after issue 50 and have been used without issue.

My theory makes sense, Kang first appeared (as Rama-Tut) in Fantastic Four #19. Even though he's changed his identity a number of times (Iron Lad, Kid Immortus, Scarlet Centurion, Kang and Immortus) I think the rights still belong to Fox. Characters change their name and costumes all the time, it's the reason why Marvel can't use Old Man Logan in the MCU for example.

As for the characters appearing in cartoons... I believe that it boils down to what sort of rights the movie studios have. For example, Fox owns the film rights to the X-Men and the Fantastic Four. Particularly with the X-Men, Fox doesn't have the merchandising rights, Marvel does. Hence why there been a dearth of X-Men movie related memorabilia, like action figures. Compare that to when the first movie came out sixteen years ago and Marvel was pumping merchandise out like crazy.

The same could be said about television rights. Marvel likely still has television rights to certain characters, so long as they are not associated with the MCU.

However, if you poke around the internet, Marvel is asking their content creators to try and avoid using characters associated with the Fantastic Four, X-Men and any other properties that they don't own the film rights. This is strictly from a merchandising standpoint.