Chiba is a server-side XForms implementation. From the Chiba homepage…

• largely conforms to the XForms 1.0 W3C Recommendation
• delivers most XForms functionality to today’s browsers
• does not rely on scriting capabilities on client-side
• adaptable to potentially any client
• support for most of the generic XForms Actions
• strong data-typing
• XForms calculation and validation with full dependency tracking
• DOM Event support
• customizable UI stylesheets, actions and configuration
• based on Java2 and XSLT
• no client installation required
• extensible Connector interface for resource-loading

Chiba Cookbook:
http://chiba.sourceforge.net/chibacookbook.pdf