I agree with flibble here: people in the RISC OS scene (with a relatively low level of awareness in such matters compared to other communities) seem to think "open source" has some vague meaning related to seeing the sources, when in fact the term is precisely defined in terms of various fairly well-established guarantees. Certainly, you can sell open source software - indeed, you can sell GPL-licensed software as long as you uphold the terms of the licence - but the notion of people paying Castle on a per-use basis shows an element of ignorance that would suggest that Castle merely want to offer the code under some kind of "shared source" agreement. If that's the way all this goes, we'll see a "shared source" licence which is actually less free than some of Microsoft's licences.
But seeing as the "few pence" per use will go towards some kind of central repository maintainer (I guess we'll see elements of current revision control trends appear in the RISC OS scene in about 2015), it looks like Castle isn't in a position to procrastinate forever on this: if the RISC OS Open people are still owed salary and Castle still needs to raise small sums which are presumably not being levied on some point of principle, my guess is that the RISC OS Open people have a stronger hand than most people previously believed. RISC OS may end up as a genuine open source project whether Castle like it or not.