I don't know if anyone here is interested, but I just finished (?) an update to the og_forum module. You can find it here: http://drupal.org/node/121822
Things to note:
-It is compatible with Drupal 5.1.
-Each group can have multiple forums
-Regular (sitewide) forums can be used side-by-side
-Group context is set whenever applicable
-Both forum and og_forum paths work - they are interchangeable
-A trip to www.yoursite.com/forum (or og_forum) will show all forums available to the user whether that forum is general or within a group they are subscribed to
-Take note of restrictions at the link above - namely restrictions on container & forum creation
-Haven't heard from the maintainer whether this will be added to cvs or not
-As noted in the link, some of this update was based on the work of others - so thanks to them
If there are any problems, post to the issue at the link above and I'll try to fix them soon.