NDK did last time someone asked (Which was not this year, but last year, so I'm sure the thread is deleted) Someone wanted to sell fics with illustrations and the offical answer was a big old no.

I've never seen charity frowned on, true. But I have also seen people freak out over people selling it. Our friend Julia got caught in a huge online wank for it, I know once, because it is. I think it is less prevalent in older fandoms, and is more an online fandom sort of thing, though. Cause that was ALL Star Trek fandom use to be.