The // in the mod Index.ini tell the game to ignore those lines.
By adding them in to Base.rte, you're having them load BEFORE the game makes the Activities.ini. CC has to load things logically; a bullet has to load before the magazine that contains it, and the magazine has to come before the gun that uses it. You have to load all the actors and their data BEFORE you can use them in Activities.ini.
Code:
AddAttackerSpawn = ACDropShip
CopyOf = Dummy DropShip
This means that you're adding an actor spawn, of type ACDropship (the usual alternative being ACRocket). CopyOf just means that it's not defining a new mod part, rather referring to a pre-existing one.
The typical followup to the above lines would be this:
Code:
AddInventory = AHuman
CopyOf = Skeleton
AddInventory means that the Dropship that we just added as an attacker will contain an object. In this case, an AHuman; the generic name for all 2 legged actors in CC. CopyOf = Skeleton is the same as the Dropship copyof.
Then you have your various weapons. Those are a second set of AddInventory, and look like this:
Code:
AddInventory = HDFirearm
CopyOf = SMG
Since this line is tabbed another level past the previous AHuman, it is known as being NESTED. Because of that extra layer, it refers to the above Actor, rather than the dropship. So, it adds a held device (in this case a firearm) to the actor's inventory. Since the CopyOf says SMG, it adds an SMG.