Sorry no1 has answered yet, the forums have been kind of dead. The main difference its that they are from different localities.
*The "arus" tend to have a blunt tail and turn most of the time fully green with white scales scattered through the body with some blue traits as well.(they are from the Aru islands in New Guinea.
*THe "biaks" tend to have a longer tail tip (lure) which turns black as they mature. Biaks, most of the time will be green with yellow blotches along the body and some white scales as well. There are 3 different type of biak bellies ive seen in my experience, black scaled bellies, yellow scaled bellies, and some blue scale bellies.
I hope this was some help, if not visit the signalherp.com website which shows you specific locations on map and how the snakes from those lacalityes look like, or just drop me an email
Coneroks1@aol.com
Carlos Echarte