Hopper is using Ogre as its graphics engine, ode for physics, OpenAL for sounds and SQlite as a database.
At the start of the project I wrote a framework using Ogre and integrating the other components. As I am doing something like extreme programming ( as far as I understood it ), everything was more or less refactored when needed. With a working version after any modification.
This is what I am doing these days : heavy refactoring and moderate additions.
I modified the Input Management, and implemented the input configuration : now joysticks, mouse, or keys can be used to control the ship !
Preparing for other stuff like video configuration inside the game instead of keeping the Ogre default way to do this ( a dialog box appearing each time the game is started ), I made my own configuration file management class.
Also, I rewrote my own GUI instead of using a hacked mini-GUI wrote by someone else.
So next, I will have to integrate these things into the project.