In case anyone is interested... here is the change to make this work (as Mike said, you will lose portability since ubb member numbers are more reliable), but you might want to do it this way....
In this block:
# UBB categories are user numbers, all others are user names
if ($authentication_type eq 2)
{
$category=$usernumber;
}
just change:
$category=$usernumber;
to:
$category=$username;
