Great question.
The virtualization server virtualizes any static HTML, JSP, or Spring-based web app (and soon, hopefully, Struts-based web apps). Each web app framework does potentially introduce some new things that need to get accomodated by the virt server, and our intent is to certify most major web app framework in demand from the Community.
Now, portals themselves are a special case of a web app framework. Portals should be treated today like we treat PHP-based, .NET-based, or Python-based (or any other type) sites. To preview these sites, you actually do not use the virtualization server; instead, you either (a) remote mount a sandbox via CIFS and set-up a preview context for that site manually, and add a custom action to redirect a preview request to the manually set up context or (b) deploy to a remote Alfresco server configured as a Staging server for previewing a future state of the site.
For script-based sites like PHP or Python, we do intend to support a virtualizing Apache server to handle these natively within the next 6 months or so (depending on other prioritiies). Until then - and now for portals - preview is best handled outside of the context of the virtualization server.
Kevin
