In theory, any programming language capable of producing Java compatible byte-code can be used with the existing Robocode engine.
The trick would be for Robocode to support the language directly - like it does with the Java and the Jikes compiler. For me when I started this was a great benefit - no need to install a IDE or SDK - just run robocode and go.
For beginners a simpler language would be of benefit - what's would you recommend?
I'm kind of thinking that Lua might be a good language to target, because it's about as easy for beginners as it gets (and a JVM version of sorts does exist ).
One other note is, I think a lot of thought would need to be put into the robot API used for this proposed project. I'm of the opinion that the existing non-AdvancedRobot APIs do a less-than-ideal job at being simple to actually use even though the API is simple, and the AdvancedRobot API is kind of messy, in part due to how it's evolved over time (backwards compatibility and such).
The original API was born from the ACM competition and was designed on purpose to be hard-to-use.
Weird coordinate system, bots being disabled after 1000 API calls...
I personally think that reverse compatibility with normal robocode is non-ideal. We could have a non-pi version of course, but building it from the ground up to be simpler on a language like lua.
I'm a high school teacher in the U.S. with a programming class. I've done a lot more with Greenfoot this year than Robocode, but with Greenfoot and Robocode one has everything needed to keep kids motivated to write code. In that sense, Robocode has been great entertainment personally and a great boon professionally. Running a local rumble server a few years ago for the kids to compete in was tremendous fun for me and them!
It would be great to provide students with an in to Robocode utilizing a language with simpler syntax and less "don't worry about these big chunks of text for now... but you need them or it won't work" type provisos. Python or Lua would be neat choices. I've got to say I'd love to see any new language choices able to work within Robocode proper though... as has been done with .Net implementation.