GNU Classpath A free replacement for Sun's proprietary core Java class libraries. [Open Source, GPL with exception] http://www.gnu.org/software/classpath/ Gnu.org~Site InfoWhoisTrace RouteRBL Check
Kaffe JVM Java Virtual Machine. Works on many platforms and includes Just-In-Time (JIT) support for most of them. PersonalJava 1.1 compliant (but does not fully support the Java 2 Platform). [Open Source, GPL] http://www.kaffe.org/ Kaffe.org~Site InfoWhoisTrace RouteRBL Check
shuJIT 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] http://www.shudo.net/jit/ Shudo.net~Site InfoWhoisTrace RouteRBL Check
GCJ The GNU Compiler for Java - compiles Java source or bytecode to native machine code. Most APIs are supported, except the AWT and Swing. [Open Source, GPL] http://gcc.gnu.org/java/ Gnu.org~Site InfoWhoisTrace RouteRBL Check
Kissme Java VM for Unix, more so Linux. Native threads and JIT compiling. Uses GNU Classpath. [Open Source, GPL] http://kissme.sourceforge.net/ Sourceforge.net~Site InfoWhoisTrace RouteRBL Check
GNU Classpath Extensions A free replacement for the "javax.*" classes (core and otherwise); sibling project to GNU Classpath. [Open Source, GPL/LGPL] http://www.gnu.org/software/classpathx/ Gnu.org~Site InfoWhoisTrace RouteRBL Check