Backdrop CMS is a fork of the Drupal project. This organization exists on Drupal.org so that credit may be assigned when Backdrop CMS developers coordinate with Drupal developers to solve issues affecting both pieces of software. The Backdrop and Drupal projects have different goals, but coming from the same original code base, there are many areas in which collaboration can benefit both projects. You can learn more about Backdrop CMS at backdropcms.org.