When extracted the mod is inside a folder named "AricsExpansion v0.9.1", but the game is looking for a folder named "AricsExpansion". Simply rename the mod folder and it will work. If you don't install with the new mod folder name, the active mod list will be incorrect, but this will not affect gameplay.
Edit: There is another error, the 'shaliq' and 'umbra' reputations were not included in a secondary dictionary named "ghostrep". In globals.gd line 696, it should be:
var ghostrep = {wimborn = 0, frostford = 0, gorn = 0, amberguard = 0, shaliq = 0, umbra = 0}
Also, I've already informed him about the mod size, it should be fixed soon.