I think an arguement COULD be made that since RiffTrax are only charging their standard rate for this - the same price they would charge for the MP3 - that they are not charging for the video. They are merely charging for their own work, and providing the video as a courtesy to those who would find it difficult to locate, convert, and/or sync. But I'm not a lawyer, either. This is between the producers of ST:NV and Rifftrax, and so far, the only thing we've heard from from the ST:NV producers has been positive. We can't really count the forum bannings, since the admins there are probably not directly connected with the productions, and may be over-reacting.
But your point is taken, sloan. I think the majority of us here know the implications of this, and certainly the Rifftrax people are aware of these concerns by now. Thanks for being so polite about it.