Google, which relies on advertising for some 95 percent of its revenue, doesn't want ads on its hotly anticipated Google Glass eyewear.

The blanket prohibition came in the fine print of a policy made public this evening, which says "Glassware" developers may not "serve or include any advertisements" and they "may not charge" users to download apps for the device.

Today's announcement, which coincided with news that Google Glass Explorer Edition prototypes were about to ship, indicates that the Mountain View company is proceeding carefully, even slowly, when allowing third-party developers access to the head mounted display's full capabilities. It also means that developers won't have an obvious way of making money from their apps.

A Google representative sent CNET a statement saying: "Developers are crucial to the future of Glass. The focus during the Explorer Program is on innovation and experimentation, but it's too early to speculate how this will evolve."

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Google has taken a different approach than other platforms have, including Apple, Microsoft, BlackBerry, and even Android: instead of encouraging native code that tends to be faster and more flexible, that approach is not permitted. The new Google Mirror API suggests that the intelligence behind Glassware will, at least for now, reside on third party servers and communicate with the eyewear through encrypted links, much like Web apps do today.

That should reduce the likelihood of crashes, malware, and unexpected battery drain from buggy software -- at the expense of limiting developers' ability to take full advantage of Glass. Voice input, for instance, is not currently accessible to developers. User interaction with Glassware is limited, and more advanced hardware features like real-time image recognition that would lead to augmented reality applications are also not accessible. (So much for the makers of Adblock Plus' jest about the Glassware they want to build.)

The documentation does say that Glassware will be able to share "photos taken by the built-in camera," display images, and with permission access the user's current location.

It's possible, of course, that advertisements from third-party developers or Google itself will eventually appear on the eyewear or a Glassware store will be created. Project Glass lead Babak Parviz left open that possibility in an interview in the January issue of IEEE Spectrum. "At the moment, there are no plans for advertising on this device," he said.

"We know a lot of you are eager to learn more about it, and I have some great news," Google developer programs engineer Jenny Murphy wrote in a post on Google+ this evening. "Today we're releasing the API documentation and a bunch of example code, so even though the API is in a limited developer preview, you can start dreaming with us."

Also released today are the tech specs for Google Glass: a 5 megapixel camera, a bone conduction transducer for audio, Bluetooth, WiFi, and 12 GB of usable memory.

Disclosure: McCullagh is married to a Google employee not involved in this project.

Update, April 16 at 9:05 a.m. PT: Adds response from Google.