Vanilla on Redbrick
Vanilla is a rather nice forum application with tons of extensions.
It is relativily easy to install on Redbrick. Also, if you have already installed Wordpress you can integrate the Vanilla logins with your Wordpress user logins (also check here if you want to also use your Wordpress template tags).
For the most part the instructions bundled with it are correct. However you will need to have an SQL account so if you don't have one email the admins.
The only difficulty is that because it's a PHP and your trying to run it on Redbrick you've got to modify the files. You need to add '#!/usr/local/bin/php' to the beginning of any PHP file that will be excuted. But which ones?
As of version Vanilla 1.0.1, the files I've found that need to be modified are:
account.php ajax/switchextension.php categories.php comments.php debug.php extension.php index.php people.php post.php search.php settings.php setup/installer.php termsofservice.php
There may be more. If you find more, please update the list above!
You can use this command on Redbrick to automatically modify the files:
perl -i.bak -ple 'print "#!/usr/local/bin/php" if $. eq 1; close ARGV if eof;' account.php ajax/switchextension.php categories.php comments.php debug.php extension.php index.php people.php post.php search.php settings.php setup/installer.php termsofservice.php
Once you've correctly modified the files, you can follow the instructions included with it to finish the installation.
I haven't tested any of the extensions nor the download updates (I suspect this won't work), but other than that it works quite well.