Stefan needs to make money too...

Just wondering...how do community names work with the forums?

I've noticed that some players with Graal# accounts have registered to the forums using their community name. If that community name changes, what happens to their forum account?

Probably nothing. You can register with any name you want, but it has to be approved by Darlene. I'm guessing Stefan just hacked vBulletin to deny all passwords that didn't match with the Graal account password (when registering) and has a script that updates the vBulletin database when you change your password.