You say "it'll contain something *like*", trouble with contracts (from what I've seen of 'em) is that they attempt to be unambiguous.
*If* the contract *did* say that ROL have an exclusive right to sell RISC OS to the "arm based desktop market" then they would have violated the license under those terms (by making ROS available under VA). As Castle have Pace's role in all this then Castle *could* terminate the license for that reason.
RO5 is based on code derived from RO3.8 (and stuff for Pheobe) it is *not* licensed to ROL (who got the license for what became RO4) while Castle got the license (from Pace) for what became RO5.
Until we get to see the *actual* contract the whole thing is conjecture - but it is significant that *all* the AMS have chosen not to put this to the test by continuing to sell products based on the OS licensed from RISC OS Ltd - I find that *quite* significant.