Refer to the download section for how to download a source release of a snapshot from CVS.
Displaytag uses maven for build and site generation. First of all, you need to download and install maven (you will need at least Maven 1.0) from maven.apache.org . Follow the instructions on the Maven site on how to do this.
It couldn't be more simple: go to the folder containing the (unzipped) source, type maven and watch the show. For this you need a working internet connection since maven will first try to download all the needed libraries (see dependencies ) from a remote repository.
Running maven without arguments will execute the default goal, which will build the library, the sample webapp, and the documentation site (this one). You can run maven -g to see the available goals. Running maven jar will simply create the library jar without the sample site and documentation.