Thanks a lot for sharing this - particularly the full source code of your implementation. It looks very clean and well written.

I personally like that you wrote your own recursive descent parser and lexer rather than using some tool to generate one. This is my preference too.

The result is that the source code makes for a great reference for anyone thinking of implementing a language on top of the JVM.

Pay no heed to the "bah humbug" comments elsewhere on this story - I think what you've done is great.