Drupal

The Drupal is an open source WCMS based on PHP and MySQL.

Several DGs are using this WCMS or they've adapted it; i.e. Capacity4Dev - the incomplete list of project partially or completely funded by European Commission @ https://groups.drupal.org/node/79093#EC

since 2012, the EC is considering to use Drupal as primary WCMS - with the project FPFIS-CMS

Source
Drupal 7 : How To (FR)