Lua in SpringRTS/Mod Structure< Lua in SpringRTS
The mod file is just a plain zipped file in the .7z format.
In this zip file there are actually very few folders and files that are absolutely required for a mod. Most files and folders are optional and just add elements to the game. For more information about the required folders/files you can read further on http://springrts.com/wiki/Mod_specification.