"All the comments about open source imply that RISC OS would be made into some sort of freeware. But this doesn't follow."
It does follow if 'open source' is taken to mean 'compatible with the Open Source Definition'.
If that isn't what you mean then it really would be better to use another term. The OSD is a very well established definition now, and using 'open source' to mean something else can only lead to equivocation and confusion.