Google has released documentation for the Mirror API, the interface that programmers will use to write services for Glass. The contents include everything from quick start guides for Java and Python to in-depth developer guides and best practices, and starter projects and libraries are available for download. The news comes just as the first Glass units are beginning to roll off the production line.

Glass is a web app

We already saw many of the implementation details in Google's SXSW presentation, but everything is presented here in much more detail. Services are "installed" by authorizing them to post to your Glass timeline with OAuth 2.0, and those apps post text, images, and other data to your device using JSON objects and HTTP requests. For all intents and purposes, Glass is a web app.

Interestingly, Google's terms of service prohibit developers from distributing their client software anywhere but "the official Google-hosted Google Mirror API Client distribution channel, unless otherwise approved in writing by Google." The switch marks a big departure from the hands-off approach Google has taken with Android app distribution, frequently touted as a strength of its "open" platform.

Not only are ads forbidden for Glass client apps, so are fees

The terms of service also explicitly forbid ads on Glass client apps, as well as charging fees for Glass. They state that "you may not charge end users any fees or collect any payments in order to download or access your API Client, or in connection with virtual goods or functionality of your API Client." It's important not to read too much into this — the terms could always change down the road — but for now it looks like all "Glassware" will be free to use, at least during the current beta. We're definitely curious about the revenue model here for developers, and we've reached out to Google for comment.

Update: Google confirms that Glass developers will not be able to charge or advertise for their early creations, but that might change in the future. "The API is still in a limited preview," a representative tells The Verge. "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."