AstroGrid webservices, and the infrastructure required to run them, are implemented in Java.
Download it here:Sun j2se page
Tomcat provides the container server in which AstroGrid's web services run.
Download it here:Jakarta Tomcat 5.0.19
Maven is used for building and deploying AstroGrid web services from source; if you are installing AstroGrid components by dropping pre-built WAR files into tomcat (the simplest option), you won't need it.
Download it here:maven-1.0.2