From John Carmack himself: the stock bots don't use neural nets [1]. It would be interesting to see what sort of emergent behaviour arises from bots that can adapt though.
The guy that wrote this is a contributor to Forbes. Anyone can be a contributor to the site as long as they write a few stories that sound like they know what they're talking about.
They stop fighting because some counter overflows, and there's no guard for it causing the application to crash. I'm sure there's smart people - or even Carmack himself - that can find the relevant code (actually, is the bot code open source or just the Quake 3 engine)?