The current stable release is version 2.2 New features are listed in the release notes.
You can download the executable jar file (recommended for normal users) or the java source files (recommended for developers).
If you are a developer, you may also want to download the Javadoc and clone the github repo.
In order to be able to run XDAT you must have the Java Runtime Environment installed on your system. Linux users can obviously use the OpenJDK Runtime Environment available in the repositories of most distros.
Current (stable) Release
This is the recommended download.
Thanks to the guys over at 3developers.de for contributing a lot of code to this release!
This was the first public release.