One of my favorite things about the SDK is the fact that it works offline. When I'm without Internet access on a train, bus, or plane, I can still develop and test my application. I usually work with my browser open, one tab pointed squarely at localhost:8080 and another open to the App Engine documentation. Until recently, the documentation presented a bit of a challenge when I was without network connectivity. But now, we've released the App Engine documentation as a downloadable zip file.
On a related note, our documentation is now licensed under the Creative Commons Attribution 2.5 License (except as otherwise noted). For full details on licensing see http://code.google.com/policies.html. As Dan Sanderson explains on the discussion group,
"These licenses permit you to re-distribute the documentation, and to distribute derivative works. For example, you can translate the documentation into another language, and distribute the translation. You can also convert the documentation to a different format (such as PDF), and distribute the new format. "
We're also planning to bundle the documentation with future versions of the SDK.