I recently heard from a user which prompted me to write this blog post. So, thanks Ryan!
Contrary to appearances, VMM is not a traditional collection of HTML files and images that can be created as a new web site on any web server. VMM is a Java web application that requires a Java Servlet Container, in this case Tomcat. I too was confused for a long time about what Tomcat is. I myself work best with analogies. Since many users who download VMM are Windows systems administrators I will compare Tomcat and a web server to ASP.NET and IIS. Although it isn't immediately apparent, ASP.NET is NOT part of IIS. It is an entirely separate process (this changes slightly in IIS 7). A typical request for an ASP.NET web application looks like:
Client -> IIS (ISAPI) -> ASP.NET
Because Microsoft tightly bundles ASP.NET you cannot run it without IIS. However, technically there is no reason you couldn't (and in fact in IIS 7, all web requests go directly to ASP.NET and IIS (ISAPI) is only present for backwards compatibility (sort of). This is very similar to Tomcat, except Tomcat is commonly used without having a web server in front of it:
Client -> Tomcat
However, there is NO reason why you cannot integrate Tomcat behind an existing web server so that it acts like ASP.NET -- just a way to process the Java requests, such that:
Client -> IIS -> Tomcat
or
Client -> Apache -> Tomcat
Integrating Tomcat and IIS is fairly straight-forward. Apache's Jakarta project hosts a document on how to achieve this supported configuration..