Here's the deal: Create something better than he does, and people use your version. If he creates something better than you do, people use his version. All copying allowed. How about that?
There was someone on here a while ago that was concerned that someone stole his app a safe a 'pro' version without ads. The advice you give here is essentially the same advice they got.
If someone rips you off, improve on it and have the better product. It's too bad that your apps are so similar -- but the concept, layout and elements are old-hat. If he ripped you off on purpose I highly doubt he'd be eager about the HN community finding out about it.
