Already very early in the Java history, around JDK 1.0.2, Ewout Prangsma (the founder of JNode) dreamed of building a Java Virtual Machine in Java.
It should be a system that was not only a VM, but a complete runtime environment that does not need any other form of operating system. So is had to be a light weight and most important flexibel system.
Ewout made various attempts in achieving these goals, starting with JBS; the Java Bootable System. It became a somewhat functional system, but had far too much native code (C and assembler) in it. So he started working on a new JBS system, called JBS2 and finally JNode. It had with a simple target, using NO C code and only a little bit of assembly code.
In may on 2003 Ewout came public with JNode and development proceeded ever faster from that point on.
Several versions have been released and there are now concrete plans for the first major version.