yep, the same trolls. i've met them and they're very nice people, but aggravating when it comes to the CKG (which btw should include an "official", but optional skill system alternative to the siege engine).
It does not have an optional skill system that replaces the Siege Engine. It has skills that you can build into your characters and uses the Siege Engine.
The High Lord, Coburg the Undying
He who sits on the elephants back
Castle and Crusade Society