@jmaasing said: But you are saying that the Dyn4J Body class should be changed to inherit Animation. That is not integration, that is rewriting Dyn4J. It is like saying that java.util.Logger should inherit from the Animation class so you can integrate logging in your animations.
(The example with Logger is just incorrect, I ignore reacting to it)
Integration is integration.
By mean of what you achieve it - is another question.
If in order to integrate something with something you should tune source code of one of this “somethings” then okay, c’est la vie.