The Github repository contains two things. First is a Dockerfile used to build a Docker image at https://registry.hub.docker.com/u/davepar/webapp2/.
The second part is a Google App Engine application for a tutorial on moving from App Engine to Docker. It's located at https://github.com/Davepar/docker-webapp2/wiki/Tutorial---part-1
If you're reading this on Docker Hub, you're looking at a Docker image that contains webapp2, it's prerequisites, and Werkzeug for running an HTTP server. The main purpose for this image is to run the tutorial, but it could be used as the basis to run any webapp2 application.