I'm working on a site running WordPress along with a vBulletin forum. The user base is registered on vBulletin. I need to allow users to appear logged in on WordPress as well for the sole purpose of posting comments with their forum user.
The user must not be replicated on WordPress, so every solution involving the creation of users in the WordPress database is not applicable.
Users recognized in this way need not have any admin or publishing privileges, only the ability to comment so that their comment appears under their forum username.
I had written a simple plugin which was working on an older version, but it's not working anymore with the most recent version of WordPress (3.3.2 at the moment). That solution relied on overriding the pluggable functions
What are the correct steps to take in order to implement this functionality?