Backdrop CMS started its existence as an offshoot or fork of Drupal. Although Backdrop originates from a common codebase with Drupal, its philosophy and organization are distinct. Backdrop practices a policy of focused releases, taking into account the feedback from the community. The overall direction is guided by the Backdrop Project Management Committee (PMC), modeled off of the Apache project.
Unlike Pressflow, Backdrop has progressed to a point where it isn't 100% API compatible with Drupal anymore.
So, do we want to handle Backdrop questions here?