On my site, users registering in Joomla are automatically registered in Anope, with the help of Adam's (not me
) live SQL build of Anope. Here's a theoretical solution for doing it the other way round though:
Have Anope write to a MySQL database. It may be necessary to use the aforementioned live build if Anope doesn't regularly write new registrations to the database, I can't remember whether this is the case. Create a Joomla user plugin. When a user attempts to log into Joomla, have the plugin check the Anope database for their username and password, and if a match is found, create and log in a Joomla user. The function &_getUser in plugins/user/joomla.php is a good example of how this can be done. You may wish to disable registration confirmation e-mails in Joomla if you're already requiring them in Anope.