org.zkoss.zul.client.rod
From Documentation
Property:
org.zkoss.zk.WPD.cache
Default: true [since 5.0.7]
It's a developing feature for ZK coder or component developer .
By default the WPD will cache after first time you load it ,
when you set it false, the WPD (the merged Widget JS Pacakge) will reload per request.