Can you please provide a concrete test or at least a description that illustrates the issue? Does this apply to JSP, Facelets, both?

The following navigation will work in stock JSF, but doesn't work in ICEfaces (both JSP and Facelets mode).

<navigation-rule>
<navigation-case>
<from-outcome>nonFaces</from-outcome>
<to-view-id>/nonFaces.html</to-view-id>
</navigation-case>
</navigation-rule>

An example of the D2DViewHandler trying to parse the non-JSF page (in JSP mode) is below:

SEVERE: Servlet.service() for servlet Persistent Faces Servlet threw exception
org.xml.sax.SAXParseException: The declaration for the entity "HTML.Version" must end with '>'.
at org.apache.xerces.parsers.AbstractSAXParser.parse(Unknown Source)
at org.apache.xerces.jaxp.SAXParserImpl$JAXPSAXParser.parse(Unknown Source)
at org.apache.commons.digester.Digester.parse(Digester.java:1586)
at com.icesoft.faces.webapp.parser.Parser.parse(Parser.java:122)
at com.icesoft.faces.application.D2DViewHandler.renderResponse(D2DViewHandler.java:517)
at com.icesoft.faces.application.D2DViewHandler.renderView(D2DViewHandler.java:152)
at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:107)
at com.sun.faces.lifecycle.LifecycleImpl.phase(LifecycleImpl.java:268)
at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:137)
at com.icesoft.faces.webapp.http.core.ReceiveSendUpdates.renderCycle(ReceiveSendUpdates.java:58)
at com.icesoft.faces.webapp.http.core.ReceiveSendUpdates.service(ReceiveSendUpdates.java:45)
at com.icesoft.faces.webapp.http.core.IDVerifier.service(IDVerifier.java:25)
at com.icesoft.faces.webapp.http.core.ViewBoundServer.service(ViewBoundServer.java:52)
at com.icesoft.faces.webapp.http.common.standard.PathDispatcherServer$Matcher.serviceOnMatch(PathDispatcherServer.java:50)
at com.icesoft.faces.webapp.http.common.standard.PathDispatcherServer.service(PathDispatcherServer.java:19)
at com.icesoft.faces.webapp.http.servlet.ThreadBlockingAdaptingServlet.service(ThreadBlockingAdaptingServlet.java:19)
at com.icesoft.faces.webapp.http.servlet.EnvironmentAdaptingServlet.service(EnvironmentAdaptingServlet.java:29)
at com.icesoft.faces.webapp.http.servlet.MainSessionBoundServlet.service(MainSessionBoundServlet.java:107)
at com.icesoft.faces.webapp.http.servlet.SessionDispatcher.service(SessionDispatcher.java:35)
at com.icesoft.faces.webapp.http.servlet.PathDispatcher$Matcher.serviceOnMatch(PathDispatcher.java:52)
at com.icesoft.faces.webapp.http.servlet.PathDispatcher.service(PathDispatcher.java:29)
at com.icesoft.faces.webapp.http.servlet.MainServlet.service(MainServlet.java:80)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:691)
at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:469)
at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:364)
at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:301)
at com.icesoft.faces.webapp.xmlhttp.BlockingServlet.service(BlockingServlet.java:54)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:210)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:174)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:151)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:870)
at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665)
at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528)
at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:685)

ICEfaces relies here on the underlying JSF implementation. I'm not sure if we want to override the default behavior?!

This isn't the default behaviour of JSF though. In normal JSF you can navigate to non-Faces resources. I've attached an example that shows this with regular JSF.

Looking at the stacktrace I can see that ICEfaces' digester (parser) is not very lenient when parsing HTML pages. A solution would be to improve the parser's ability to recover from this kind of issues.

Regarding the issue with forwards to any kind of resources, such as images or PDFs, there's more work to be done here. Because ICEfaces updates the page with DOM diffs received on Ajax connections it can't just reply with the content of the resource (with the corresponding headers) like a vanilla JSF implementation would. It's quite hard to imagine a DOM diff between a *.iface page and an *.gif.
A solution to this problem would be to send a 'page reload' message to the bridge and when the browser will reload its current URL the framework would dispatch the request to the resource declared in the navigation rule. This strategy preserves browser's current URL thus simulating a real server-side forward.

Fixed using the solution described above.

A regression is caught after the change of behavior for the navigation handler, now the following exception caught in Tomcat:

SEVERE: Parse Fatal Error at line 1 column 63: White spaces are required between publicId and systemId.
org.xml.sax.SAXParseException: White spaces are required between publicId and systemId.
at org.apache.xerces.util.ErrorHandlerWrapper.createSAXParseException(Unknown Source)
at org.apache.xerces.util.ErrorHandlerWrapper.fatalError(Unknown Source)
at org.apache.xerces.impl.XMLErrorReporter.reportError(Unknown Source)
at org.apache.xerces.impl.XMLErrorReporter.reportError(Unknown Source)
at org.apache.xerces.impl.XMLScanner.reportFatalError(Unknown Source)
at org.apache.xerces.impl.XMLScanner.scanExternalID(Unknown Source)
at org.apache.xerces.impl.XMLDocumentScannerImpl.scanDoctypeDecl(Unknown Source)
at org.apache.xerces.impl.XMLDocumentScannerImpl$PrologDispatcher.dispatch(Unknown Source)
at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanDocument(Unknown Source)
at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source)
at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source)
at org.apache.xerces.parsers.XMLParser.parse(Unknown Source)
at org.apache.xerces.parsers.AbstractSAXParser.parse(Unknown Source)
at org.apache.xerces.jaxp.SAXParserImpl$JAXPSAXParser.parse(Unknown Source)
at org.apache.commons.digester.Digester.parse(Digester.java:1785)
at com.icesoft.faces.webapp.parser.Parser.parse(Parser.java:122)
at com.icesoft.faces.application.D2DViewHandler.renderResponse(D2DViewHandler.java:539)
at com.icesoft.faces.application.D2DViewHandler.renderView(D2DViewHandler.java:152)
at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:107)
at com.sun.faces.lifecycle.LifecycleImpl.phase(LifecycleImpl.java:268)
at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:137)
at com.icesoft.faces.webapp.http.core.JsfLifecycleExecutor.apply(JsfLifecycleExecutor.java:18)
at com.icesoft.faces.webapp.http.core.ReceiveSendUpdates.renderCycle(ReceiveSendUpdates.java:57)
at com.icesoft.faces.webapp.http.core.ReceiveSendUpdates.service(ReceiveSendUpdates.java:45)
at com.icesoft.faces.webapp.http.core.IDVerifier.service(IDVerifier.java:25)
at com.icesoft.faces.webapp.http.core.ViewBoundServer.service(ViewBoundServer.java:52)
at com.icesoft.faces.webapp.http.common.standard.PathDispatcherServer$Matcher.serviceOnMatch(PathDispatcherServer.java:50)
at com.icesoft.faces.webapp.http.common.standard.PathDispatcherServer.service(PathDispatcherServer.java:19)
at com.icesoft.faces.webapp.http.servlet.ThreadBlockingAdaptingServlet.service(ThreadBlockingAdaptingServlet.java:19)
at com.icesoft.faces.webapp.http.servlet.EnvironmentAdaptingServlet.service(EnvironmentAdaptingServlet.java:29)
at com.icesoft.faces.webapp.http.servlet.MainSessionBoundServlet.service(MainSessionBoundServlet.java:117)
at com.icesoft.faces.webapp.http.servlet.SessionDispatcher.service(SessionDispatcher.java:36)
at com.icesoft.faces.webapp.http.servlet.PathDispatcher$Matcher.serviceOnMatch(PathDispatcher.java:52)
at com.icesoft.faces.webapp.http.servlet.PathDispatcher.service(PathDispatcher.java:29)
at com.icesoft.faces.webapp.http.servlet.MainServlet.service(MainServlet.java:76)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:691)
at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:469)
at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:364)
at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:301)
at com.icesoft.faces.webapp.xmlhttp.BlockingServlet.service(BlockingServlet.java:54)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:204)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:174)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:151)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:874)
at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665)
at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528)
at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:689)
at java.lang.Thread.run(Thread.java:595)

The attached test does not have a properly defined web.xml. ICEfaces framework is not exercised at all.
Also, it would be more handy if the test case is a war ready for deployment.

missed <redirect/> in original test application