Leigh Klotz, Xerox Corp: A host of other [XForms] implementations are available or in progress, but my pick for most interesting is DENG, which is an XForms to Flash compiler written in Flash. DENG supports XForms, SVG, RSS, XHTML, and CSS.
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DENG is an award-winning, open source Modular XML Browser, capable of rendering subsets of XHTML, SVG, XForms, XFrames, arbitrary XML (e.g. RSS) and any other custom XML application, styled by CSS 3.
The footprint of the DENG Modular XML Browser is 76 KB, allowing zero-install, cross browser and cross platform deployment of existing and emerging W3C standards to the vast majority of today's web browsers.
DENG integrates into host HTML documents, AJAX applications and applications leveraging the Adobe Flash Platform (such as Flash and Flex), is extensible and easily customizable.
DENG is released under the GPL.