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I know that Zope can be used with a Apache as frontend, but it is listeing to port 8080 like Tomcat.
I don't know how you'd set up the Frontier server as a proxy, though. Are you sure it'll only run on port 80? The Frontier documentation talks about a setting "user.inetd.config.http.port" which you can use to specify the port it listens on. If that works, it'd be simple to set up the Apache server to act as a proxy instead, using mod_proxy.