Briefly: one of the two (or three?) fora that were eventually merged into OS-Dev was a forum on a message board called Mega-Tokyo, originally hosted on Geocities IIRC. [...] I am not sure how it came to host an OS forum, but I assume that one of the mods had an interest in the subject.
If I may?
Mega-tokyo.com was host to a static website called the "OSFAQ"
(the origins of which I was told once, but have since forgotten). Naturally, discussion of the OSFAQ, individual projects spawned off it, and additional information became part of the site forum
Eventually I annoyed df enough to host a PhpWiki on his site, so errors and shortcomings of the OSFAQ could be fixed by anyone, not just himself. I actually administered that Wiki installation for a while. That gave a definite boost to things, and became the foundation of what the OSDev.org wiki holds today