Another developer is offering Wolfire Game's Lugaru HD title on the Mac App Store for 1/5 of what the official game is selling for. How? As per the terms of the Humble Indie Bundle a while back, Wolfire decided to open source the game, though not its assets or characters, and the other version on the Mac App Store is an outright copy with assets included. Kotaku tracked down the developers, who apparently don't believe they've done anything wrong, saying that "we have every legal right to market and sell the software, and we feel that $1.99 is a fair price." The official version sells for $9.99.
The worst part here is that Apple obviously approved the app, and as of this writing has not yet taken the app down. Wolfire hasn't yet heard back from Apple, and a spokesperson from the company says only that it's looking into the matter. Then again, issues of intellectual property are often left to developers to negotiate outside the App Store. This is an unfortunate instance where the App Store could clamp down on obvious infringement.
The case seems pretty clear-cut -- Wolfire did open source its title, but it also made clear that it retained rights to all of the assets. Since it's fairly apparent that those are being used in the "unofficial" release, I'd expect Apple to take the offending version off of the store soon enough.