rdenk144: yes you are wrong. The meaning of "exclusive" depends upon where it is in a sentence, as I took the liberty of explaining. Read my answer again.
If ROL have rights to sell RISC OS 4 and RISC OS 5 is derived from 3.XX, then Castle have not broken any contract, as 5 is not derived from 4 but from 3.XX. As ROL doesn't have access to RISC OS 3.XX code, only RISC OS 4, then I would assume that they only have rights, exclusive or otherwise, to RISC OS 4. Therefore, it is highly unlikely that Castle have broken any contract by selling another version of RISC OS to the desktop market.