johnpettigrew > "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."
The specification would be the license granted to ROL (with respect to the use and sale of RISC OS) by Element 13 (Acorn RIP). If my memory (hopefully unclouded by Hamburgers from the past) is correct the public comments at the time was that ROL was licensed to sell and develope DESKTOP OS products, but that they were prohibited from selling products that would directly compete against Pace (who had bought the rights to the OS in full from E13). Bearing in mind that Castle later acquired the whole shebang from Pace (the then OS owner) then Castle would be interchangable with Pace in the license that ROL had.
ROL would (If the above is true) be obliged *not* to directly compete against Castle (formerly Pace). But ROL would still be allowed produce a desktop product under the license.
As I am not a lawyer I won't charge my usual fee and you may need to take a lot of the above with a pinch of salt.
Comment of the day: Puzzlement comes with age.....