jarc's build.xml makes some assumptions about tomcat which I don't have installed; I changed build.xml to point to my copy of javax.servlet.jar in order to compile jarc. I think it's ok (license-wise) to package the servlet jarfile along with your project so people don't have to go hunting for it.

You mention on the sourceforge page "Therefore web apps with the Arc html.arc package won't work. " - arc's web server doesn't actually use continuations, it uses closures, so they probably should work on jarc.

The proper symbol to declare for atstrings is "atstrings"

  (declare 'atstrings t)