I just sent this to Will vie email:
Okay, I figured out how to make it work:
In wp-content/plugins/openid, rename wp-login.php to wp-login2.php
Then modify openid.php:
require_once ‘wp-login2.php’;
I think the wp-login.php in the top level was getting included instead of the one in the plugin directory. Of course, I don’t really know what was intended, so I might have messed things up. But at least now I see the OpenID login option on the login page.