As for metafiction vs. fanfiction — I *do* think there’s value in having different terms, rather than lumping all derivative stories together, because not all of those derivative stories are talking to the same audience or trying to accomplish the same thing. I personally would reserve the term “fanfiction” for the intensely social realm of fandom, where the stories can be in conversation not just with the source material, but also with the fans and the other stories those fans have told (both about the source, and about other things). And I agree with your take on “metafiction;” I would use that word for fiction that is aware of its own fictionality in some fashion. That’s a different conversation, but it’s a cousin to the fanfiction one, and sometimes they overlap (as in the case of “The Chuck Writes Story”).
