Yes that should be safe, it doesn't modify the database if thats what you mean. Regarding group visibility, at the end of that file you'll see /* Display */ Return, replace that with: /* Display */
$visibleToGroups = array(2,4); // 2 = Guest, 4 = Default Admin group
return (in_array(\IPS\Member::loggedIn()->member_group_id,$visibleToGroups) ? $this->output( $members, $memberCount, $guests, $anonymous ) : '');Add more group id's to that $visibleToGroups array. EDIT: You could do the opposite way if it's more suitable so you don't have to edit for new groups. /* Display */
$hideForGroups = array(2); // 2 = Guest
return (in_array(\IPS\Member::loggedIn()->member_group_id,$hideForGroups) ? '' : $this->output( $members, $memberCount, $guests, $anonymous ));