> even if a fanfic author is given an automatic permission to write a derivative work, it still is fan fiction?
very simply. legal permission does not count as approval of the work, its only permitted- as distinct as allowing a plumber entry and calling them a friend.
> when is fiction a fanfic and when it is not?
maybe, not a fanfic when the author gives SPECIFIC approval before release. written w/ only blanket permission (license) isnt approving the specific work.