These instructions for integration of vBulletin were taken from posts by SteveB from the forum.
This extension allows for shared user credentials, meaning that you can create your account on vBulletin and use it to log into MindTouch Deki with it. Also, vBulletin groups can be used to map vBulletin user rights to MindTouch Deki user rights. However, it does not do single sign on.
Enter the following configuration settings:
You'll need to import groups and assign roles to them to finish up the configuration, but that's the same as for other authentication providers.
Once that's done, a new drop-down box appears when you try to login. Select it and enter your vBulletin username and password. And voilà you are logged in with your vBulletin credentials!