Development of Creative Commons licenses

["Elf M. Sternberg" <elf.sternberg AT speakeasy.net>]

I'm looking for a licensing option and I'm not sure which one is exactly 
right.  I have a large SF story archive that I have under a creative 
commons Attribution-NonCommercial-NoDerivs2.0 (which is more or less 
what I've been using, in one form or another, since about 1990).

Several of my fans would like to publish their role-playing materials 
based upon my stories.  I would like to be able to make that material 
public, using an Attribution-NonCommericial-ShareAlike2.0.

I appreciate that there's a very fuzzy line between an RPG module and a 
narrative story, but is there a reasonably clean way to make this 
distinction?

Elf