Run multiple programs within a single JVM. [Open Source, LGPL]

Multiple process Java execution environment that can run on top of a standard JVM (with limited support) or on top of a Java Operating System kernel with native hooks to support multiple processes. rheise.os provides an API for managing processes, users and security. [Open Source, LGPL]

Essentially a program manager for Java (which is itself a Java application). It allows you to organize your Virtual Machines, class libraries, and Java applications using an intuitive graphical interface - no more pesky editing of classpaths! [Open Source, GPL]