I found a minor problem with group legend in forum index.
Go to ACP:
Create a closed/invisible/open group named: "FORUM_OWNER"
Go to language/xx/common.php
Set the dedicated language key:
'G_FORUM_OWNER' => 'Forum Owner',
Save file, back to acp => group overview:
Yes, you can see the translated group: Forum Owner
Go to your forum index/group page:
The group must be special instead of closed/open/invisible to benefit the translation cuz we see something like that in index.php/memberlist.php
$group_name = ($row['group_type'] == GROUP_SPECIAL) ? $user->lang['G_' . $row['group_name']] : $row['group_name'];
I suggest to replace $row['group_type'] == GROUP_SPECIAL by isset($user->lang['G_' . $row['group_name']]) so it allow administrators to internationalize their groups name without jumping in database to set groupe type to special (3).