I don't think their uses are that different, though. They were both designed to be flexible extension languages for programs written in a different language, an

I don't think their uses are that different, though. They were both designed to be flexible extension languages for programs written in a different language, and were strongly influenced by Scheme. In particular, Javascript's JSON seems semantically identical to Lua's table notation (just with different braces in different places). Lua is used as a data serialization language as well (see the notes about Petrobras, for example), and the compiler has been tuned specifically for vacuuming up data files. It's also good as a ready-made config file format.