You can find the full source code for this website in the Seam package in the directory /examples/wiki. It is licensed under the LGPL.
Yes. In fact, that is a big part of the secret sauce in JBoss Seam. You can extend the EL to resolve names in any context you can think of (JMX, LDAP, EJB3, etc.). You extend the EL by implementing an ELResolver. See the JSP 2.1 JavaDoc for details on the ELResolver interface. The ELResolver is typically installed in a ServletContextListener. With JSF 1.2 it can be installed using the <el-resolver> tag in faces-config.xml. This is all enabled out-of-the-box if you use Seam.