You must, of course, download the source distribution of Java Treeview from http://jtreeview.sourceforge.net

The java sdk can be downloaded from the sun website at http://java.sun.com/j2se/.

Apache Ant, the build tool, is available from http://ant.apache.org/bindownload.cgi

The crossplatform editor jedit is recommended, available from http://www.jedit.org/index.php?page=download

Docbook is more of a file format (an XML dialect to be precise) than a tool.