Released version 0.21 to tracker. I am planning to put a demo moodle here, once most other features will have been completed. For now, you can look at the static HTML demo and if you wish, download the version in the tracker for testing.
There were a couple of issues with the current quiz/questions. The most pressing one is that the Edit/Add Questions page seems to absolutely require a question category as a parameter. It would fit the workflow much better if a category could be unspecified once entering the question editing page with a new question. Then, the user would have to think about categories at least as much as to select the default category from the list. The changes required to do this seemed too dramatic so they should probably be discussed with Tim Hunt/the community. For now, we are preselecting the default category for the user.
Some highlights: To get quiz work as designed, I added a new GET parameter to the question editing page, which allows specifying the name of a GET parameter to return a newly created question’s id to the page in returnurl. Also, the quiz editing page got a new get parameter, addonpage, for specifying the page on which to add a new question.