But, provided that STD's computers provide a desktop (i.e. run RISC OS 4!) there should be no trouble with their licence from ROL. There's no specification of the market within which RO4 may be used - only that it should be desktop, not embedded or otherwise cut down. If someone other party is saying that ROL's licence doesn't stretch as far as they thought, that could be the two third parties mentioned.
It would be a Very Bad Thing for the RO market if Castle suppressed the marketing of ROL's products for any reason. Castle could well survive on specialist uses of their hardware and accompanying OS, but that doesn't do us lot any good