Rick Broida/CNET

AppGratis, a service with 10 million users that offers a free or discounted app once a day on Apple's App Store, has been mysteriously removed.

The software disappeared from the App Store late last week, Pocket Gamer reports. That's despite being approved, and on Apple's platform, since last December.

AppGratis began as "an email newsletter shared among friends," before evolving into a business. The company brokers deals with developers to make their software free for 24 hours, something that can help get unknown apps discovered, and potentially even boost their profile in the paid section of Apple's rankings when the sale is over. Similar services include FAAD and AppiDay, which still have apps on Apple's store.

The company picked up a $13.5 million round of funding in January, and was growing by around 100,000 new app users a day, TechCrunch noted at the time. In a blog post in February, the company reported reaching 10 million users.

An Apple spokesman told CNET the software was removed for breaking two of the company's App Store guidelines:

2.25: Apps that display Apps other than your own for purchase or promotion in a manner similar to or confusing with the App Store will be rejected;

5.6 Apps cannot use Push Notifications to send advertising, promotions, or direct marketing of any kind.

The removal is notable because it's the latest such App Store discovery app to be pulled. AppShopper, a popular database of iOS apps that would also alert users to price changes, was removed last December. That was on the heels of the change to Apple's App Store Guidelines in September, which added 2.25, or no "similar to or confusing" rule.

Complicating matters is the fact that Apple acquired app discovery service Chomp early last year, though shut it down a few months later. That service was designed to help users sort through what was becoming an increasingly large volume of apps on the App Store, as well as Google's Play Store, by using keywords.

AppGratis' removal is the latest from Apple, which requires that any software sold on its App Stores matches up with its content guidelines before being published. That hasn't stopped a number of controversial apps from making their way through before being removed. It's typically more of an issue when the app in question potentially competes with Apple's business, or does something better.

(via TechCrunch)