That game has fees (initialized at 1%, I haven't checked to see if that's changed) so I wouldn't exactly call it a zero-sum game, but it does look like an interesting game, and a quick look at the contract doesn't raise any obvious red flags.

A well-designed website definitely makes things more interesting, not to mention making it easier for someone with a less technical background to play. The game you linked literally just gives the JSON ABI and instructions for playing from MyEtherWallet. A website, maybe with lightwallet built-in so you can connect to any public RPC node, would make it a lot easier to play. Me personally, I can play from the geth console.. but I don't really consider that user-friendly.