Drag and Drop questions developed by Open University are very popular question types among the Moodle plugins database in the question type category. There is a Moodle Tracker issue opened last year to put all Drag and Drop question plugins into Moodle Core i.e. MDL-47494.
The tracker issue is specifically focused on adding these plugins:
The good news is that the issue is resolved and is waiting review before being added to the repository. The questions will be integrated in the upcoming Moodle version i.e. Moodle 3.0