A scammer is trying to cash in on the Because We May indie game sale.
So just to make this clear: while the Android edition of Canabalt HD is official and fully endorsed by the original developer, Adam Saltsman, the version of the game currently available on the App Store is bogus. Not only is it a knock-off, it's not even HD. It's just a cheaply upscaled version of the original title.
The knock-off version is being sold by Picks Mano, whose other projects are mostly image collections with titles like Car Wallpaperz and Happy Birthday Wishes. The release of Canabalt HD almost perfectly coincides with the Because We May indie game sale, which is supposed to promote freedom for developers to sell their games at whatever price point they like.
Much like Lugaru HD which was also ripped off by enterprising thieves, Canabalt is technically open source. While this means that the game's source code is free to download and tinker with, the game's artwork, music and sound effects are all propriety, making this unlicensed version illegal.
While knock-off apps crop up on the app store all the time - though the service isn't quite as dicey as Google Play for Android, which frequently features outright malware - they're usually pulled almost as quickly as they appear. Still, it boggles the mind how this, or indeed something as obvious as Pokemon Yellow, can make it through Apple's app approval process.