Those guys are hunting the unicorn. You cannot generate more energy at the cost of less energy. However, you can transform energy and waste some as heat in the process. Such machine is impossible. The pendulum will slow down intil it stops.Very memorable!
For those interested in reading the thread in question: http://forum.allaboutcircuits.com/showthread.php?t=2741
Makes interesting reading.
What that guy is trying to do would be like having a motor and a generator sharing the same shaft and having the motor fed by the generator (a closed loop system).