Scripting Layer for Android (SL4A) brings scripting languages to Android by allowing you to edit and execute scripts and interactive interpreters directly on the Android device. These scripts have access to many of the APIs available to full-fledged Android applications, but with a greatly simplified interface that makes it easy to get things done.
Web site: http://code.google.com/p/android-scripting/
Source code: http://code.google.com/p/android-scripting/source/browse/
Code license: Apache License