I don't know about AEG, but with WotC the unspoken (actually, somewhat spoken -- I think Ryan Dancey said it) rule was:
a) If you're claiming to follow the license(s), you need to do it right.
b) If it's a fan creation, and you're not claiming to follow the license(s), and if you're not reproducing the owner's material, and you're not making money off of it, probably no one's gonna hassle you for it.
AEG has been pretty darned good about WLD, btw -- if I'm remembering right they allowed folks to modify and post player-versions of the WLD maps. And the maps aren't even open gaming content.