KSSC supports Zdoom wads, however you must do the following to enable NPC's in zdoom to work:
You must have at least the community build of Zdoom (.97 or something like that..)

Create a basic decorate actor and in its properties add this token:
ConversationID
Followed by a number. The number will represent the Mobj ID. Like if you create an decorate actor with ConversationID value of 5. When you create your script, in the MOBJ field, add 5. Then press use on the actor and the dialog will start.


Using decorate items:
Here is a basic decorate item for script use:

ACTOR SpecialItem : Inventory 19010
{
	ConversationID 282	//tells the script to use this item #
	+COUNTITEM +ALWAYSPICKUP 
	Inventory.Amount 1
	Inventory.PickupMessage "Something happend.." 
	States
	{
		Spawn:
			BKEY A 1
			Loop
		Death:
			BKEY A 1
			Stop
	}
}

You can have the NPC sell, give, or drop this decorate item with the value of 282.
For example in the script:
GIVEMOBJ 282 will cause the npc to give this item after choosing the reply. 

-kaiser