... Is the quality of this "Dahon" Boardwalk as good as the real thing? All I want is a cheap and simple folding bike I can keep around and use once in a while for years to come, and the Boardwalk S1 seems to fit the bill.
I believe you got just what you wanted. Performance Bike is listed as an authorized Dahon dealer on the Dahon web site. There is a thread discussing "grey market" Dahon Boardwalks on the Dahon Rider Forum in the General Discussion section. See:
http://www.dahon.com/forum/index.php?showforum=13