JESS and CLIPS use essentially the same language, so either one is fine for the tutorial. CLIPS' home has moved around a bit, it looks like http://sourceforge.net/projects/clipsrules/files/CLIPS/6.30/ is the most recent one. 
JESS can be downloaded as a 30-day trial version, but you can extend that if you have the code word from “Jess in Action” (the book written by Ernest Friedman-Hill, the developer of Jess).

Tags: tutorial, JESS, CLIPS