[Dev-luatex] (no subject)

Hello, I couldn't figure out, how I can get access to the luatex-sources. My concern is: I'm developing a music-score language, as of now called "emil" (= easy music input language), which is likely to move towards Lua. (Hans: we had a short conversation in Darmstadt, if you remember). I am curious to see, how luatex communicates with the tex-interpreter. I'm at the beginning and my first problem is, to get Lua-output as a scannable string back to the calling interpreter. Hans' luatex-manual points out, that luatex has this already built in. So my question: can I get access to the sources, or get a hint, how to output Lua to the calling interpreter, Thanks in advance Christof