I could inform you of what I know since I joined, remember i'm starting from about two years ago, so other veterans will have to fill in the rest from before then.
Before 2006, The Hive Workshop was under a different domain name. I can't remember exactly what it was, but the site was mainly for the 40K clan members, and people interested in Warhammer 40K TD.
That is where this all started, with that Tower Defense. Ralle created Warhammer 40K TD, and along with it, this website.
The domain name was finally settled on as The Hive Workshop because the decision to have the site focus on resources, mapping, and world editor use, and because the Hive demonstrates its Warhammer roots.
The site has always had a frontpage, although one quite different than what you see now. We used ImPortal and PHPBB2, for any interested, and the site ran like a dream.
We only had several thousand registered members, and only 4 thousand of which had more than 10 posts. Regardless, we were a small community, everyone knew everyone else very well, and the staff had a great relationship with the users.
Now, we expanded into a resource based site, Ralle added the maps section (I was the first moderator along with another guy by the name of Deckboy), and things were swell. This is around July 2006 btw.
Archian had joined the site in early April/end of March 2006, and had become a valuable asset to the growing site.
The summer passed with little fanfare, as far as I recall, the site continued to grow, and in October 2006, Wolverabid joined with us and proved himself invaluable, rapidly rising through our ranks.
Christmas 2006 was a time of great change, as a dying wc3sear.ch merged with the Hive Workshop to preserve its halls of knowledge and resource.
This brought many, many, many thousands of noobs to our site asking "AH MAH GAHD WHERE WC3S?!?!?!?!!!?11!1!1?!1/!" and then even more complaining about how the Hive was inferior in every way to their beloved (now dead) website. They soon got over it, we managed to sort out the files from wc3s, and slowly began to rebuild the databases of resources, adding to our own, and moderating 144 pages of maps that got brought over from the merge.
Due to the massive load on the servers with the influx of new members, we were forced to switch from very cheap shared hosting to renting a server of our own for dedicated use. This was very costly, and the donations program was set up in order to provide the money needed to keep the server going, as Google ads were not bringing in enough.
The front page and resource sections were redone, and things took off from there. In February 2007, the Chat Room was added, and the site has slowly grown in size, feature, and resources.
I'm sure I missed a few things (plus the whole 2005 and previous era), but that's the general premise of what's been happening here for the last two years.