- A "template engine"; a generic tool to generate text output (anything from HTML to autogenerated source code) based on templates. It's a Java package, a class library for Java programmers. Latest stable release is 2.3.13, 2008-05-05.
- This project provides a harness to build the source code from the OpenJDK project using Free Software build tools and provides replacements for the binary plugs with code from the GNU Classpath project. Latest stable release is 1.9, 2010-09-10.
JCR - Java Code Reviewer
- A web-based tool for performing and managing code reviews. It can be used for code in any language, but provides some extra features for Java.
Jetty Java HTTP Servlet Server
- An open source, standards-based, full-featured web server implemented entirely in Java. Latest release is 6.1.19, 2009-07-01.
Jython Home Page
- Jython is an implementation of the Python language written in 100% Pure Java, and seamlessly integrated with the Java platform. Latest production release is 2.5.1, 2009-09-26.
Kaffe.org - Kaffe Virtual Machine
- A clean-room implementation of the Java virtual machine, plus the associated class libraries needed to provide a Java runtime environment. Latest release is 1.1.7, 2006-03-27.
The Castor Project
- Mapping framework between Java objects, XML documents, SQL & OQL databases and LDAP directories.
The SAXON XSLT Processor
- A cross-platform, open source XSLT and XQuery processor. Latest stable release is 18.104.22.168, 2008-07-02.
Vuze - BitTorrent Client
- An advanced multiplatform BitTorrent client written in Java that includes a tracker and a torrent maker components needed to run a BitTorrent solution. Internationalization is excellent: available in ~ 40 languages. Latest release is 4404, 2010-05-08. Formerly called Azureus.