Just thought i'd let members know that there is an alternative to the hacked RS discuss forums that works, with one very minor modification, on MU.
I happened upon Simple Forum V1.0 today -
http://www.yellowswordfish.com/
And was pleasantly surprised to see it work almost immediately out of the box on Wordpress MU.
The only issue i had was it looking for the users table in the blog i was running it on (this one in question was blog id 3).
A simple fix to this was to go into the
sf-includes.php file and around line 18 you should see
'define('SFUSERS', $table_prefix.'users')'
This is setting the plugin to look for your blog id's user table but MU stores all these in one user table.
So just change
'define('SFUSERS', $table_prefix.'users')'
to
'define('SFUSERS', 'xxx_users');'
where xxx is your table prefix. In my case my prefix is wp_ so
'define('SFUSERS', 'wp_users');'
And that was it. Up it went and ran like a dream.
It even has a BBCODE type input box, post moderation and informs you in your admin panel when new posts need moderating.
Its a bit green around the edges visually, but nothing some CSS won't cure.
I see he hard coded user pictures, but i'm seriously considering whether this would be prime for something like Gravatar to be included.
Anyway hope someone gets some use out of it. I'm off to continue testing it.
Now i can offer my members two different types of forum, woohoo :)