The INET Framework lives in the inet-framework/inet repository on GitHub.
master: Holds the current stable version of INET (as of Jun 2015, version 3.x).
integration: Contains the codebase for the next major version of INET as it is being developed (as of 2015, version 4.0)
topic/<name>: Temporary branches opened for the development of a particular feature. Topic branches may be deleted, rebased, or their history rewritten at any time.
attic/<name>: Abandoned topic branches. They may be dead, or just resting.
Note: Most people contribute by forking the repository on GitHub and submitting pull requests to us.