Any work for CE will involve changes to the Windows specific code and user interface, it's irrelevant to RISC OS.
Just as irrelevant as fact that all the OS's run on the same processor. Firefox is written in C and compilers can spit out code for any processor. The problem os RISC OS is so privative compared to the other OS's, CE included, a vast amount of work has to be done to provide the facilities the application expects.
Unixlib provides these facilities, but in it's current form it will never allow applications to run at speeds comparable to other OS's on the same processor. There are too many layers because RISC OS is just too different, and feature poor.