I have re-worked my private forum hack for Xoops 2.0. Since mike [mvandam] has the notifications in the core, there is no need for a monitoring hack so this one only contains the alterations to private forum behaviors.
Also in this version of the hack, all of the behaviors are optional, so you can mix and match. X2's configuration options make this very easy.
Here are the behaviors: 1) Assign rights to private forums by user groups 2) Allow searches, views, to display private forum posts for those who have rights only. 3) Optional block configuration to display private forum posts and include poster information.