I can only offer a link:
Credence: Thwarting P2P Pollution
There you can find data and the full client code.
Maybe you could ask the initial developer if he could add you as developer in the Sourceforge project.
Besides: If you want Credence to become adopted, implementing it in Phex looks like the way to go. LimeWire didn't adopt it last time, and they are unlikely to adopt it now, except if they receive pressure from other clients using it and providing better results.