As the WiQuery project page says, version 6.x has been compiled against Wicket 6.x, so you won't be able to use it with Wicket 1.5.
The latest WiQuery version compiled against 1.5 and available in Maven central is 1.5.8.
Pregunta
Which WiQuery version is proper for Wicket 1.5.10? Is it WiQuery 1.5.8 (the last from 1.5.x branch) or can be used the new version 6.6.0?
Solución
As the WiQuery project page says, version 6.x has been compiled against Wicket 6.x, so you won't be able to use it with Wicket 1.5.
The latest WiQuery version compiled against 1.5 and available in Maven central is 1.5.8.