The Helsinki University of Technology has released X-Smiles 0.93, a proof-of-concept XForms engine written in Java. It isn't very polished, but it does run on most platforms. I'll be using this for demos in my XForms session at Software Development 2005 West next week. This release cleans up various parts of the application, though a lot of work remains to be done.
Chiba 1.0, an open source, web-based implementation of XForms based on servlets and XSLT, has been released. Chiba enables XForms to be used in current browsers without plugins or special requirements on the client-side. Chiba is published under the artistic license.