Through Android Open-Source Project (AOSP), Android 2.3 Gingerbread source code has been released. The push is still not completed and developers and hackers are asked to wait for hours or days in order to keep the servers from going down.
“Even though Nexus S is designed to be suitable for AOSP work, there are some caveats. I very strongly recommend against trying to use Nexus S for anything related to AOSP at the moment. Trying to unlock or use your Nexus S for AOSP work could easily turn it into a Nexus B (where B means “brick”); I have two of those, they’re not very useful.”
There you have it, folks. For more information, visit the Android Building|Google Groups forums.