Sorry, I could have sworn that this document used to be linked on that page and didn't double check.
http://www.google.com/url?sa=t&rct=j...,d.cWc&cad=rja
I can't seem to find the RDK-BDC-BDC24-UM package you need to build the non-FIRST firmware. Maybe somebody will have a copy laying around they can get to you. I'm not sure if the VexPro factory default firmware implements the tokenization or not:
http://www.vexrobotics.com/vexpro/mo.../217-3367.html
No, there is intentionally no documentation on how the FRC firmware communicates. It uses a proprietary tokenization scheme that is not published. See page 15 of the Getting Started guide for slightly more detail.