clearspring - the widget network.

The Kernel, also called Launchpad Advanced, is the core client-side component of the Clearspring platform. It is intended for advanced users who want all of the capabilities of the Container, but want greater control over how they use it, the appearance of the user interface, which assets load first in the page, and more. It is available for use with numerous web widget development languages, and exposes the In-Widget API.

Check out the Container vs. the Kernel for an explanation of alternate options, or just jump right into the API