To practice within New York State, a professional must be licensed and REGISTERED.
Practicing a profession without a license and current registration is a felony in New York State.
However, until now, Knapp has never mentioned on CHSCA website, Knapp Family Counseling (KFC) website, Facebook pages, Twitter posts, and LinkedIn group that his registration expired one month ago. He continues to use "LMSW" title which he cannot use now. On CHSCA website, there is a list of services offered by CHSCA: http://thechsca.org/what-we-do/services-we-offer-you/item/48-services-we-offer-you. It includes therapy as currently available service. On his KFC website, there is a page "Available Services & Fees": http://www.knappfamilycounseling.com/available.html where he states: "I offer individual and group counseling via office visits, phone, and online." He did not make any corrections or changes on that page. I think these mean that Knapp continues to provide therapy. There is no indication that he is currently not available as a therapist. If he continues to practice, his actions are not only unethical, but also illegal.
I do not think he forgot that he was required to renew his registration in order to continue to practice. I think he did it intentionally. He is under investigation by NYS Office of the Professions because his former client filed a complaint at him: http://tossandripple.blogspot.com/2011/01/john-m-knapp-lmsw.html. Probably, he did not renew his registration in order to avoid their punishment for his ethical violations toward his former client. However, if he continues to practice now, this is even worse because it is a felony.
Update (posted on August 6, 2011): I just learned that Knapp renewed his registration and now his status appears as "Registered." When I checked his license information a couple days ago, he was not registered. So, even though he is registered now, he practiced without registration for over two months.