Old permission hook

To get the Bypass permission to work you have to change
(d6 version, multilink_redirect.module)

function multilink_redirect_perm() {
  return array('bypass multilink redirect');
}

to
(d7 version, multilink_redirect.module)

function multilink_redirect_permission() {
  return array(
    'bypass multilink redirect' => array(
      'title' => t('Bypass multilink redirect'),
      'description' => t('Override the redirection and shows a message instead'),
    ));
}

Clear cache after that and you should see the option in the permission list.
Cheers!