If one was to write using a pen-and-paper Role Playing game covered by the Creative Commons License would it be classed as fan fiction or some other genre of niche work?
That depends on the type of licence - as I understand it, a creative commons licensor can choose how to let someone else use their work, if at all, so you would have to approach them about it. They might say you can adapt their ideas for non commerical use, as long as you give them credit for the original idea, so you could publish a story using role play characters and worlds that were under licence as long as you didn't profit from it. On the other hand, they might state that you cannot adapt or modify their original creation at all. Either way, you need to approach them.
From what I've seen yes I am allowed to do derivative non-commercial works. My question remains as to what would this be classed as, is it fan fiction or some other category?
If you can't publish it for commercial use, do you need to worry about the genre? But if there is a category of fanfiction for RPG then that's what it would probably fall under.
'genre' has nothing to do with this... 'fan-fiction' is not a 'genre'... fan-fiction can be any genre [horror/romance/sci-fi et al.] you seem to looking for a legal definition... and that could range from 'fair use' to 'plagiarism' so if that's the case, you need to ask a literary attorney for an answer...
I wouldn't call it fan fiction, necessarily, unless you are using character and/or storylines from existing works. If you're using an RPG-universe that is released under the license, but with plots and characters entirely created by you, then that starts to get away from fan fiction, in my view. But the line is blurry - I'd probably call something set in the Star Wars universe "fan fiction" even if it met these criteria, whereas when someone writes a story involving the Cthulhu mythos, we generally don't see it as fan fiction, and in fact there is a long history of authors publishing such works.
When you say "a pen-and-paper Role Playing game" do you mean simply a set of rules such as D20, or do you mean an actual scenario? If it's just the rules then a story that conformed to those rules probably wouldn't be a derivative work. If it's an actual scenario then a story that played out the scenario would be legally tricky.
