I can verify that dannymk's implementation works (see reply above). I replied to his post with a patch that helps it be a little more forgiving of the data entry for OpenID URI's.
OpenID is gaining quite a lot of momentum, and it would be great to see it officially supported as an authentication method in WebGUI.
OK, I spoke with Brad Fitzpatrick and he told me that he is working on an upgrade. When the new Net::OpenID::Consumer is available we will be able to cover all the 2.0 requirements. If anyone knows of another available perl library please let me know. Brad will post upgrades to his module at his blog: http://brad.livejournal.com/