I have asked many times for the source from author, Podatron, but he doesn't seem to like the idea. I use Symbos on the MSX-2 and with a disassembler under an emulator you get quite far without the sourecode, especially if you start by studying the source code to the apps on the system. Luckily the system is very small (as is the memory on these machines), so with a few weekends of tinkering you can find your way around in it.