I don't think they are gonna sue anybody.
In fact, if they checked out Rifftrax, they would see that they are in good company over here as far as riff targets are concerned. They should be honored that they were chosen.
At worst, they may ask for the mixed version to be removed and have only the MP3 version for sale, with the unriffed video made available as a free download for those that need it.
But these are Trek geeks, so who knows how they would react.