I included instructions on acquiring the JWSDP, because a lot of readers will not be exposed to the latest versions of the JSTL through Tomcat 5.x, because they are not using that Tomcat version yet (particularly when the book was published in Jan 2004). The JWSDP is a reference implementation that includes Tomcat and JSTL 1.1, so it is an easy option for downloading and getting acquainted with JSTL 1.1.

In addition, there are some examples later in Chapter 23 showing how to use the c:forEach tag with a java.util.Map, such as Example 23-8, pg.568, which uses c:forEach with a java.util.SortedMap; and recipe 23.13, which uses c:forEach with the "cookies" JSTL implicit object, a java.util.Map type. We should have referenced you from the c:forEach introduction to these examples later in the chapter. Example 16-8 on pg. 367 shows how to use c:set to place a new value into a java.util.Map object; again we should have forward referenced (or back referenced in this case!) from the JSTL chapter.
In general, it's important to include some recipes that might seem too basic for some readers, to assist newcomers.
Finally, thanks for the correction on the WEB-INF/classes path. I even use that path in the web application that provides the basis for the book. Aaaargh!

Bruce