The newly-published terms and conditions for developers working on Glass also prohibit companies charging for apps. The glasses, which have a five megapixel camera and voice-activated controls, have started to be shipped.
The first devices will go to developers and "Glass Explorers". Google held a competition earlier this year inviting potential users to come up with ways to use the device, while developers have been eager to be among the first to try out the technology.
As part of the announcement, Google also gave the first official details of the device’s specifications. The bone conduction transducer allows the wearer to hear audio without the need for in-ear headphones – sound waves are instead delivered through the user’s cheekbones and into the inner ear.
The company promises a battery lasting for "one full day of typical use".
Its display is the equivalent, the company says, of looking at a 25in (63cm) high-definition screen from eight feet away. The device is able to record video at a resolution of 720p.