The reference has also been included in the spec directory.
Include the js file, then run
stemmer(<word to stem>) to return the stemmed word.
You can get a trace as to what is going on, corresponding to the steps outlined in the papers, by provding a second argument of "true" and using one of the browser debug consoles.
stemmer("hopefully", true) will output
1c /^(.*[aeiouy].*)y$/ hopefulli, telling us that rule 1c was matched
by that regular expression and as a result, we got hopefulli.
As of Sept 6, 2012, PorterStemmer1980 is 100% compliant.
There is a demo available here
Available over here.