This is a development setup, not intended for production. It is intended to be used as a local (Badgr)[https://github.com/concentricsky/badgr-server] server in an scenario in which Badgr is used as a dependency. One such case is (PaperBadger)[https://github.com/mozillascience/PaperBadger], but it can be used for any other projects. This is not a development environment for the Badgr server itself, but a way to easily run the server within a local setup to be used as a dependency. As such, the Badgr sources are hosted within the container (not shared with the host), the latest code on github (at install time) will be pulled in, and the installation relies on a local sqlite3 db.
The instructions to install Badgr are not very clear, so this container may be pulling in more (hopefully no less) dependencies that it actually needs.