Originally was ESWAT's (Ontario team) forum, which became the main hangout for Canadian players. The biggest/main forum at the time was probably Airsoft Zone (ASZ) which was in the US. After C67 passed in '98, so ~1999-2000, the classifieds on ASZ became hard to use for Canadians -- who couldn't import anymore and could only deal with other Canadians. Coupled with the fact that one of ESWAT's members, Tru, was an early retailer in Canada... the forum became the hot spot for airsofters in Canada.
Faced with this growing popularity (and now being more of a hub for all Canadian players than just a team forum where friends hung out), the forum was reborn as Airsoft Canada -- around 2001. Everyone who was on the previous forum migrated to ASC, so the oldest join date will be 2001. But if IIRC there was an interim incarnation of ASC before the switch to the current forum software.