The latest release of dyn4j adds a number of new features. See the the release notes. It also contains a number of important bug fixes. On the other hand, the API has been changed slightly and may break code written against older versions.
The Sandbox app has also seen some changes. Many bug fixes along with the features in dyn4j have been added. In addition, the threading issue on some platforms has been resolved by using the Newt-AWT bridge offered by JOGL. This makes the app far more efficient at handling input. The Sandbox includes precompiled tests along with the declarative (xml) tests. This allows the deprecation of the TestBed application. The Sandbox will take its place as the sole testing application.