Because the downloads and binaries for the Physics Body Editor / Box2D editor do not work on modern versions of Mac OS X / Java 7.x, here is the recompiled binary.

Run with:

java -jar physics-body-editor.jar

This does not yet work with Java 8 (issue with Java 8 and LibGDK). If you have Java 8 installed, here is a version which includes the Java 6 runtime so it will work always.

Using Physics body editor files in actual games; https://github.com/fundead/BodyEditorLoaderXNA