Java VM for Unix, more so Linux. Native threads and JIT compiling. Uses GNU Classpath. [Open Source, GPL]

JIT plugin for the Sun JVM, for Linux and FreeBSD on x86 processors. Includes support for a transparent distributed object system, MetaVM. [Open Source, GPL]

Open source research infrastructure for dynamic compiling and memory management; supports programs compiled to bytecode and linked with GNU Classpath libraries. [SourceForge, Open Source, Intel]

Article by David K. Friedman and David A. Wheeler. It briefly introduces Java, provides a bit of Java history, and describes various Java implementations.

Open source implementation of the Java runtime. Includes links to other open source resources.

Port of Kaffe to the BeOS platform. [Open Source, GPL]

Information on getting Java (Kaffe) to run on Amiga computers.

Java virtual machine (VM) that runs in Linux kernel, Linux kernel module JVM, based on JOS and kissme projects. [Open Source, GPL]

Combines the jJOS kernel and decaf virtual machine. [Open Source]

Sun Microsystems backed industry body, Java Community Process (JCP) oversees development of platform and language, voted to alter community structure, officially supporting OSS implementations of Java, JCP 2.5. [The Register]