Korken,
I also tried my hand at making the chain and noticed it was a bit unclear in the original example as to how the bone went completely around -- but I think the trick is that path is actually wrapped around the shape of the path twice, so the part of the path that goes the second time around is laid at the same spot as the first part. This makes it appear as one path but gives you the extra 50% you need to move the bone back to the start position. This isn't easy to describe and a bit tricky to do but if you need more help I have some notes on it, or perhaps someone with more know-how might step in and describe it some more.
On the other hand, I also noticed another thread here in the forum recently talking about pulleys/chains, etc., that simply took a circlular model and used a distortion modifier in an Action to make it into the shape of an ellipse to make it look like a chain. Rotating the original bone worked fine on the new shape. It seemed a heck of alot easier to implement.
-Jim