Checkout the whole project from CVS by running:
cvs -d:pserver:anonymous@cvs.sourceforge.net:/cvsroot/displaytag login cvs -z3 -d:pserver:anonymous@cvs.sourceforge.net:/cvsroot/displaytag co -P displaytag-all
(When prompted for a password simply press the Enter key)
Displaytag uses maven 2 for build and site generation. First of all, you need to download and install Maven (minimum required version 2.0.1) from maven.apache.org. Follow the instructions on the Maven site on how to do this.
Go to the displaytag-doc folder, type
mvn install
and watch the show. For this you need a working internet connection since maven will first try to download all the needed libraries from a remote repository.