To build this applet you will need:

All of the instructions to install and configure the tools are available on their respective websites.
To those versed in using Ant, compile the project via the build.xml as you would do for any other project. Use the makedistro (the default) to generate everything or jar to get a usable jar file. Post queries on the forum if you're having trouble.

The source code can be obtained either via SourceForge's files section or by accessing the CVS directly.
Instructions on how to use the CVS server is available too.

The JDK (Java Development Kit) is available from the Sun Microsystems Java website. Instructions on installing, updating and configuring are available there.

Apache Ant is a make-like tool available on all major platforms. I've used it as it simplifies the copying, compile, jar, XSLT and zipping process to release this project. I still suggest that you use an IDE for development work though.
Also, who can resist a technology that uses their name!