Welcome to Oerth
Though based on the Greyhawk boxed set(s), this campaign has been running for over 20 years. As such, there are some differences described in detail in the wiki.
Additionally, I started with other editions (red/blue box, 1st edition, 2nd edition). I’ve got a fair amount of house rules; I’ll see if there’s a good place to upload them here. Reminder to players; see the Mesh folder for full details.