AMS: "Let's see. The bulk of RISC OS is written in densely written ARM Assembler (a specific processor), the effort to recode it to either another Architecture (x86 ?) or even to a High Level Language (C/C++) so as to gain portability would be - to be frank - a complete waste of what limited resources are available."
If you have the source you can feed it in to a cross assembler and have that spit out code for any other architecture. With a couple of passes you can even optimise the nasty 2 operand register poor x86 junk resulting from our beautiful ARM instructions, although going straight to the slightly less crap x86/64 would be a better idea. This would result in a factor of 5x-15x better than the best emulator JIT, or around 1/3/ to 1/2 the speed of hand coded native assembler, which would compare very well to the result of re-writing it in C.