[Dave]

It's because of the check that checks if the current IP matches the $serverip variable.
You probably want it to be something like this in that case:

PHP Code:

<?php 
require('./global.php'); 
require('includes/functions_login.php'); 
   
// Post get items 
$username = urldecode($_GET['un']); 
$password = urldecode($_GET['pw']); 
  
// If no info specified 
if(is_null($username) && is_null($password)){
    die('No login provided.');
} 

$result = verify_authentication($username, $password, md5($password), md5($password), '', false);
  
// Final get id 
if($result === true && !(strpos($username, '@') !== false)){ 
    if($vbulletin->userinfo['usergroupid'] == 8){ 
        echo 2; // Banned 
    }else{ 
        echo 1; // Not banned. 
    } 
}else{ 
    echo 0; // and if all else fails, the shit you provided is wrong so return error 0
}

Then you execute it as follows: http://example.com/script.php?un=Dave&pw=password