Java Virtual System (JVS) is built around a virtual file system (VFS) - a common platform of Java, by Java, for Java. JVS extends JVM and makes it from an interpreter running half-compiled code a first-class server.
Luxor is an open-source XML UI Language (XUL) toolkit in Java that lets you build UIs using XML and includes a web server, a portal engine (supporting RSS), a template engine (Velocity), a scripting interpreter (Python) and more.