Credit Due is an admin theme that emulates the WordPress admin UI. They created a UI that many users prefer to work with, and those Wise Programmers deserve credit for creating such a user-friendly design.
This was created to help with organizations reluctant to migrate to Drupal 8 because they prefer the WordPress UI,. It's also for organizations with existing WordPress sites that have functionality needs better suited for Drupal, but a user base accustomed to WP.