The quake 3 source has been out for years. I used it as a helpful hint when converting C4 to support similar network structure and repeatable physics.
The Doom3 gameplay code (moddable) and quake4 gameplay code (moddable) also show in detail how they do their game physics and majority of the network systems behind the snapshots.
If I could get C4 working properly with the collisions I want and the networking i want, then it wouldn't be hard (just alot of time) to build WF4 on top of it. The problem is: ALOT OF TIME.