I'm looking at the wayback archive now.... Looks like Terran probably had leadership problems. The board maybe even lost it's domain name for awhile? I don't know. It seems fine in 2003. But then in 2005 it's like a domain-parking webpage. Then in 2008 it's back, but without the old database? Then in 2009 it's gone for good?
The forum says it had 600 members in 2003, then 200 members in 2008 (which is why I assume they lost the old database.) So they were definitely losing members. It also seems like there was never more than a few people online at the time. So I would guess people got board, they couldn't hang on to traffic, and several bad server/domain changes killed what little traffic was holding on. There were probably like 3 people left when somebody stopped paying the bill. That's my guess.