This project aims to provide a publicly available space for tintin++ development outside of the main development at http://tintin.sourceforge.net/, which does not offer a version control system, bug tracker or any other form of contribution other than sending patches and hoping for inclusion into the next release. In this sense, it might even help with official releases by show-casing the usefulness of these tools.
That said, this project does not aim at creating a fork of tintin++. The main development should still happen upstream.
Within this project /trunk will contain the latest official version from http://tintin.sourceforge.net/. Nothing else should go there.
Everything else happens on branches. Every project developer can have their own branches, or can decide to work together. Every developer is responsible for how they manage their branches. However, branches should be merged with incoming changes from new official releases.