The cube given out to winners of Apple&39's annual design awards.

Mac OS developers who want their application to be in the running for an Apple Design Award now face an extra hurdle in that process: making sure the app is on the Mac App Store.

As part of this morning's dating and detailing of its Worldwide Developers Conference in June, Apple quietly announced that only apps published to one of its two App Stores would be eligible for consideration as part of its annual design awards ceremony.

Developers who don't have their applications in Apple's nearly four-month-old distribution marketplace, either by choice or because their app did not pass Apple's review muster, now have until May 23 to get them up to be considered.

For iOS developers this part of the process is nothing new, as the App Store on iOS is the only way Apple allows applications to be distributed on the platform. But for Mac OS X developers this marks a dramatic shift in the way Apple is treating the open software distribution model that has served end users since the platform's beginnings. This also limits the breadth of applications that can be considered for the competition given that the Mac App Store requires users to be running OS X 10.6 (Snow Leopard) or higher.

Apple began its annual design awards program in 1997 under the moniker the "Human Interface Design Excellence," changing to its current name just a year later. Those who win get promotion on Apple's developer site, as well as a cube-shaped award that glows when picked up. The design for that cube, which has been made by Palo Alto, Calif.-based Sparkfactor Design since 2003, was once put through a CT scanner by an award winner to see how it worked.

This year's WWDC runs from June 6-10, and is taking place at the Moscone Center in San Francisco.