From the website:

RSF is an open source web programming framework, with roughly the scope of Sun's JSF. RSF is written in Java, and is built on the Spring framework. RSF features a pure-HTML templating engine named IKAT, which achieves the cleanest separation between presentation and logic yet made - build "components" using pure HTML and libraries of code rather than heavy framework base classes. RSF also features a lightweight request-scope Spring clone, RSAC, which brings the magic benefits of inversion of control into the request scope. RSF currently has integrations for Hibernate, JSR-168, Cocoon and Sakai

This could be a good model for us since it is a very very clean separation of logic from layout. Makes widgets available to <div> containers in XHTML.