The source code directory structure for Restful Objects is as follows:

trunk/
  main/               # main release for Restful, including Maven site
    applib/             # the Restful application library, for client-side code
    viewer/             # the Restful viewer implementation
    documentation/      # this documentation
  support/            # Support for application developers
    release/            # defines dependencies for projects using the 'viewer' submodule
    archetype/          # (placeholder)
  testapp/            # application for testing - not released
tags/
  main                # tags for trunk/main
  archetype           # tags for trunk/archetype

As is usual, to ensure that tags go into the correct location when releasing, the mvn-release-plugin plugin has been configured (using <tagBase>) to override its default location.

You can checkout the entire trunk using Subversion:

svn co https://restfulobjects.svn.sourceforge.net/svnroot/restfulobjects/trunk ~/restfulobjects/trunk