It looks like someone might integrate Tapestry 4.0 into AppFuse before I get a chance. Now that Tapestry 4 has reached Beta 3, this seems like an excellent idea to me. My only request is to not make the initial Tapestry 4 integration depend on JDK 5. I plan to start working on AppFuse 2.0 in September and it would be nice to have Tapestry 4 in AppFuse 1.9 as well as 2.0. I'd love to start this next month, but I'm attending OSCON and working on Spring Live for most of the month.
P.S. The main reason I'm writing this post is to send a trackback to the developer who wants to do this work. I was unable to leave a comment on their site, nor find a contact e-mail address.