Has the wording of the complete license that ROL operates under ever been made available for public viewing?
If it's as air tight as you believe, ROL would surely have protected itself by using the legal system in the past.
If not it would normally just have to accept the situation, so as to not cause further damage to their own business, or the general business environment. This is what I found most confusing with ROL behaviour.
Ref your link, I would direct you to the "RISC OS Open's response" at the bottom of the article. I think Steve says it all.