Lua is the program and code used by many servers you see: wittebolx, kamuix, and any server that has commands for you to use that have some tangible reaction in the game. This is like a turret spawning in front of you, buying a tank just by saying !buy apache or some such similar commands. In this post I will explain how you can make a server with these abilities.
Stable V1:
Download the stable V1. Just put the files into your FDS directory and edit the ssgm to add LuaPlugin.dll to the Plugins list, edit the luaplugin.lua file with scripts to create the 'special' commands for your server. Crimson Editor or some other code viewer is recomended over Notepad, get it here.
Beta V2:
Video tutorial on the installation of Lua V2.