According to MacRumors, the GM release is the final version that will be shipped to customers and can be used by developers for testing against iOS apps.
The iOS 6 will be available for free download on September 19th.
The new features of the operating system were presented at the live keynote held by apple last Wednesday.
They include a new Maps application with turn-by-turn directions, Siri improvements, the new Passbook app and others.
The iPhone 4S, 4, 3GS, new iPad, iPad 2 and 4th generation iPod Touch will support the iOS 6.