Bot Epidemic has posted a Q&A with Ryan "Ridah" Feltrin, talking about the AI and bots (or lack thereof) in Kingpin. There's also this bit that's of note for would-be Kingpin mod authors:

Cube: Is the Kingpin source code going to be appearing soon, or is the intention to have the game patched a couple of times to remove any lingering bugs before a release?

Ridah: That's the intention. I expect to have the code out within a week, but that depends on how things go with the patches.

BE has also posted a new version of Ridah's Eraser Bot (version 1.10). This is the version that appeared in the Quake II add-on Extremities, and features "heavily re-worked CTF and combat AI," as well as a new route-file for Q2CTF2. This is a patch for the Win32 version of the Eraser bot only.