The earliest records of activity can be seen on the internet archive Wayback Machine website. The first archived page/s they have on there date to December 12th 2004.
The second record on the site dates to January 29th 2005.
These are a matter of public record and can be found at: Internet Archive Wayback Machine
Also, When the site was hacked many years ago (due to the previous owner running PHP-Nuke, another free, poorly engineered script), the hackers very kindly archived their handywork on their website.
Their hack was effected on the 26th March 2006. You can see this at: this hacking site.
So, on and off there has been activity at Ham Radio Forum.Com for nearly six years now, as opposed to the two years of activity at hamradioforum.net
By the expression 'on and off' I accept the fact that there may have been occasional periods of downtime due to script changes, and server problems, but even hamradioforum.net suffers from outages from time to time as can be seen recorded here Ham Radio Forum • View topic - Whoops - regarding Site Outage (on their own website), and also mentions of that site outage can be found on Twitter:
Twitter / Paul: HamRadioForum.net is free. ...
Twitter / Paul: @m0bov 99% up time, but wh ...
Also found these comments at James Ridout (m0bov) on Twitter
73, JethroSmythe.