I hate to keep returning to this verse as an example, but SCP comes to mind as a comparison for what you, Oliver, are specifically addressing: the idea that, if the original piece of media allows people to make offshoot works, that this permission immediately validates all of said works.
SCP, functionally, does this, with one exception: for us to accept such a page, it must be accepted onto the SCP wiki. Same for tales or anything else, it has to be brought into the fold, even though anybody can make their own SCPs building off of what every other author has written.