If there isn't any documentation for the translation system in the Docs folder, I'll have to write some. It's pretty simple. Stepmania uses the two letter ISO 639-2 codes for the language files. When the theme or engine needs a string, it looks it up by section and string name in the file for the current language.
< maxvg1> shakesoda: then why do i still play lol
<@shakesoda> because you're an ITG player. And thus, a masochist
<@shakesoda> Kyzentun: I think you might need to put down the meshes for a bit