The surviving 8th edition source has code for Chaos networking included:
https://www.tuhs.org/cgi-bin/utree.pl?file=V8/usr/sys
It does not appear to be included in the man pages.

Was Chaos networking in use at the labs, or is it just an artifact present on the surviving tape?

Related to that, I’m interested in the Chaosnet implementation for 7th edition. Dave Moon's Chaosnet memo includes this intriguing sentence when talking about the V7 implementation: “The NCP is entirely implemented in the kernel as a device driver”.

I could not find that source code in the TUHS archive, nor on Kirk McKusick’s DVD. Does anybody happen to have it?