SceneBuilder uses $APPDIR in its Info.plist:

  <array>
    <string>-Djava.security.manager</string>
    <string>-Djava.security.policy=$APPDIR/Resources/scenebuilder.policy</string>
    <string>-Dfile.encoding=UTF-8</string>
  </array>

With b08 I get a SecurityException at startup which is the sign the policy file has not been found.
When I modify the Info.plist to replace $APPDIR by "/Applications/JavaFX Scene Builder 2.0.1.app/Contents" then the exception goes away.