UnorderedSet cannot be used

Try spelling DOpus.

vbscript is not case sensitive

Yes, you are right... seems indeed to be a problem

function OnClick(clickData) {
	var cmd = clickData.func.command;
	var tab = clickData.func.sourcetab;
	cmd.deselect = false;

	var vec = DOpus.Create().Vector(tab.selected_files);
	
	var ss = DOpus.Create().StringSet(vec);	
	DOpus.Output(ss.empty);
	DOpus.Output(ss.count);
	
	var us = DOpus.Create().UnorderedSet(vec);
	DOpus.Output(us.empty);
	DOpus.Output(us.count);
}

This is a bug on our side. We'll fix it in the next beta. Apologies for that!