Il faut patcher le module Drush et plus précisement le fichier wget.inc dans
<drush install folder>/drush/commands/pm/package_handler

Ajouter simplement à la ligne 56:

$release['download_link'] = str_replace('ftp.', '', $release['download_link']);

N'oubliez pas de supprimer le hack dès que ftp.drupal.org est à nouveau disponible.

Using drush when ftp.drupal.org is down

ftp.drupal.org is down. It is still possible to download projects from the Drupal website but you need to use http://drupal.org instead of http://ftp.drupal.org in the project url you want to download

With drush however, you need to look a bit further to make it happen.

You need to patch the Drush module and more precisely the file wget.inc in
<drush install folder>/drush/commands/pm/package_handler

Simply add at line 56:

$release['download_link'] = str_replace('ftp.', '', $release['download_link']);

Don't forget to delete this hack when the serveur is up again !