As a avid commodore computer user and 8 bit guy watcher, porting Petscii Robots to the CE would be a hefty undertaking as you would have to write it from scratch. Petscii robots was written in assembly for the MOS 6502, the CE uses the Zilog eZ80 processor. As one could imagine, the two systems cannot exchange code directly from one another.
For the second question:
I hate to sound like Mateo, but you have to grasp the limitations of computer hardware. A c64 emulator under an emulated JVM, while it would be cool, would run slower than a Lada full of elephants going uphill against a 400 mph wind. There is a c64 emulator for the TI 68k series, however as one could imagine it's not that great. A JVM emulator is just adding another layer of work onto that, and is therefore completely pointless. So yes, it sounds dumb. But try to make an emulator if you want to, it'd be really awesome!
To summarize, a Petscii robots port is
possible. However you would need to put a lot of work into it. Right now I'm working (not really working b/c school and lazy) on a port of M.U.L.E. for the CE and I can tell you that porting a game is not easy work. It requires dedication and good programming skills. If you feel like you're up to the challenge, disregard everything I just said and do it! It would be really cool.
Best of luck,