Yes, Jarc works with AppEngine. I've been learning AppEngine the last week or so. The CGI-style JarcServlet in the current release, jarc2, isn't an efficient way to go for AppEngine, so I've written a new JarcServlet that loads a single .arc file at init time which defines methods for each URI. I haven't done a new Jarc release, but if you pull the code from CVS, you can get the new JarcServlet. See webapp/servlet.arc for my test code.
I haven't tried, but according to http://groups.google.com/group/google-appengine-java/web/wil... they support jruby, groovy, jython, rhino, scala, and others, so I don't see why not. It might not be possible to use arc's native webserver if appengine obliges you to go through the servlet api. If that's the case, you'll need a few lines of actual java to make that happen - basically a stub implementation of Servlet that delegates the request to arc. Let me know if you want to try that, I'll be happy to help.
