SableVM is a Clean room implementation of Java Bytecode Interpreter implementing the Java virtual machine specification, second edition.
This JVM is a rather new project that was started from the ground up to build a robust, extremely portable, efficient, and fully specifications-compliant (JVM spec, Java Native Interface, Invocation interface, ...) Java Virtual Machine that would be easy to maintain and to extend.
The core engine is an interpreter which uses state-of-the-art techniques to deliver performance that can approach that of a "naive" just-in-time "JIT" compiler, while retaining the software engineering advantages of interpreters: portability, maintainability, simplicity.
The simplicity makes SableVM's source code very accessible and easy to understand for new users/programmers.
SableVM is Free Software licensed under the GNU Lesser General Public License (LGPL). It also makes use of Classpath (copyrighted by the Free Software Foundation FSF) which is licensed under the GNU General Public License with linking exception.
SableVM is being developed by a team of hackers who contribute to the project. Besides mailing lists developers can usually be reached via and IRC channel on irc.sablevm.org (irc.freenode.net alias) #sablevm.