XML-Convert is a tool to help convert OpenITG/NotITG song-specific xml files into lua files. In theory, it should work with any OS that can run lua, but it's only been tested on linux.
Requires lua 5.1+ and luafilesystem:
luarocks install luafilesystem
To run, pass in the name of a folder, and the converter will recursively scan for .xml files to convert into .lua files.
lua xmlconvert.lua ~/Games/Stepmania\ 5/Songs/MyPack/MySong/
The outputted lua files may not work out of the box, but they will certainly be closer to working than the .xml files were.