Backdrop CMS is the Drupal fork. Based on the familiar APIs of Drupal 7, Backdrop provides a more compatible and affordable alternative to upgrading existing Drupal sites.
The one-sentence description of Backdrop features is "Drupal 7: With Panels, Views, and Configuration Management in core". But at version 1.4, there have now been over 5 releases of Backdrop. It is loaded with lots of new demanded core features, like built-in auto URL aliasing, redirects, and in-browser downloading of new projects. Backdrop includes new administrative theme, dozens of UX improvements, and improved APIs. But at the same time it provides an upgrade path (via update.php) and maintains a high amount of compatibility that allows modules to be ported in as little as an hour. Backdrop may feels like the next version of Drupal, but with a different name.
Hundreds of sites are now running on Backdrop CMS. Come and see if it's a match for your next project!