After some efforts with Jbuilder, I can conclude that it's not the best IDE for the project. So I installed Eclipse and I checkout the project.
When the branche is all downloaded, how can I start to work with it? I don't know Eclipse and I don't want to lose days on configuration. Il make a project called nukes with the repository, so I should now maybe tell him wheres are the src directories... but I don't find anything for that.