Amun does not have a backend like normal CMS instead it provides an RESTful API with that you can manage all aspects of the CMF. The authorization is made via OAuth. We have written a sample backend application in Java but you are free to implement a backend in the language of your choice like Javascript, PHP, ASP or any other language wich is capable of making HTTP requests and parsing JSON or XML. This is a list of available backend systems for Amun. If you have written a backend or want to start please get in contact with us.
Zubat is a backend writte in Java. It is a prototype for debugging and testing Amun and it is also a reference implementation to see how you can access the RESTful API. You can download the current version of Zubat at the project page. The source code is also available.