No, it is NOT a mod that adds furry creatures* into CSGO. It is support for scripting using Squirrel, a VScript language for CSGO.
Simply download the repository as a ZIP and extract to your CSGO folder. Once you have the necessary assets installed, you need to place the "csgo-squirrel-mod" prefab in your map.
*You could make something like that with this mod, though.