My guess is that this remote-control app will come free with the 'new packaged version' of the ipod (which is just the regular version ipod with a remote control thrown in the box). Since users are paying for a new ipod to get the remote control (and the remote-control application), this would effectively skirt the Sarbanes-Oxley Act - since this is not a 'new feature', but an already existing feature.
Existing users of an ipod would probably have to pay for a the remote-control app since this would be a 'new feature'.
My take is slightly different, although you're on the right lines... This is why the update to 2.0 has to be a paid for update for those of us with version 1 iPod Touch units. You pay for that upgrade and, as part of the additional functionality, get the app store. This application then provides the free software as part of its design. In this way you get around the Sarbanes-Oxley Act as the new stuff is an extension of a new feature (app store) that you've paid for... good lord that's confusing, hope it makes some sort of sense.