Open Jdk

OpenJdk is an OpenSource FreeSoftware project based on source code released by SunMicrosystems. Sun released most of the source code of its Java Platform Standard Edition, version 6 (though some was restricted by third parties.) As of 2009, the Java community uses the OpenJdk project to develop code that will satisfy the compatibility tests for version 7 of the Java Development Kit specs. It has also developed an open source version of JDK 6, available for Linux and OpenSolaris?.

OpenJdk contains source code for the HotSpotVm, a JavaLanguage compiler, and a suite of class libraries.

http://openjdk.java.net/

The OpenJdk project also hosts closely related codes, such as the DavinciMachine project.