1) Download and install Maven. Follow the instruction at http://maven.apache.org/download.html
2) JBoss repository have moved to a Nexus server, and you should follow the instructions in the page Maven repository - Users common for all Jboss projects to add public JBoss repositories to Maven settings.
3.3) Build RF from sources:
Just checkout sources from 3.3.x or 4.x branches and execute mvn install from root folder in order to build.
More information about RichFaces project svn repository structure and build itself:
General information available about JBoss Maven repository: