The latest stable release version is 1.0-beta-4 (released 18 Aug 2007). It can be downloaded from the Codehaus Repository.
The latest snapshot distribution can be downloaded from the Codehaus Snapshots Repository.
To use JET components in a Java application that supports Maven, simply declare the dependency
groupId=org.codehaus.jet
and artifactId=jet-regression
or jet-hypothesis
and the appropriate version. Maven will automatically add to the classpath all the required components.