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.
An EL Function maps to a static method. The function is typically defined in a TLD. See the Unified EL Spec and the FunctionMapper class in the JSP 2.1 JavaDoc for more details on EL Functions.
A list of functions built in to the Unified EL can be found here.