What do you mean by does not list the Forum application. When I open the URL given, it just redirect me to www.myhost.com. Have you download the package yet, or are you trying to install it from the repository? If it's not in the repository, I advise you to download it through cvs and place it in your /package directory. You can use this command to download it from cvs. This is for the HEAD.
cvs -d :pserver:anonymous@cvs.openacs.org:/cvsroot checkout forums
You can see all the packages available through their cvs directory
http://cvs.openacs.org/cvs/openacs-4/packages/#dirlist
