CirclePack, the software for Chapter 6 of Explorations in Complex Analysis, was created by Ken Stephenson and is an open source Java program under GNU public license. The software and scripts for Chapter 6 are provided here; you may also visit the author's web site or circlepack.com (under construction) for further information.
It is recommended that you download the software and all scripts in the archive CirclePack.zip: put "CirclePack-J2.0.jar" on your desktop and the scripts in some directory. CirclePack should start from the desktop with a double click (it requires Java 1.6+).
Alternately, you can download and run CirclePack from a browser via Java WebStart: just click CirclePack.jnlp and follow the prompts.
However you start CirclePack, you can then load scripts into its "ScriptFrame" from your local machine or open its internal browser and navigate to script (*.xmd) files on the web. When a script is loaded you can go through it with the "NEXT" button or open, read, modify, and save the script.