Integrate Lithium Forums with Drupal?

Hi. I've played with Drupal 6 somewhat and am considering it for a fairly big site. However, it's a requirement that we continue to use the existing forums, which are hosted by Lithium.

I have not found a lot of information on integrating Lithium forums with Drupal. Obviously, users and groups would have to be integrated. Additionally, styles should match, but this is less of an issue since they can be styled separately to look the same, and updated in coordinated fashion.

How much work would be involved in integrating Lithium with Drupal? Would this be a matter of taking an existing forum integration module, and altering it to work with Lithium? How big a task would this be?

Any advice or pointers to further information would be appreciated. I've not found much info on my own so far. There's a lot of sites which mention Drupal and lithium batteries, which doesn't help.