Yes, but that refers to "TRAVEL TRANSACTIONS", or worded alternately, spending money while there, and not to travel itself. Per technical wording of the law, one can technically go there legally by boat and not spend money, bringing all of your food, etc etc and not purchasing souvenirs while in the country. However, US Customs will assume you must have spent money there if you were there unless you can prove otherwise, a "guilty until proven innocent" situation. One of the often referenced solutions to this is to take on a Canadian crew member and have this person make all purchases and have proof in form of receipts, etc, to that extent.
All of this being said, certainly the safest course is to wait and see what happens now given the position of our government and the newish leadership in Cuba.
That is too risky a situation for my blood. Further, the linked site that I provided above has this.
"Cuba has announced that as of May 2010 it will start requiring visitors to have non-U.S. medical insurance, and will sell a temporary policy to those who do not have it
Not sure how a US citizen is going to keep from spending money there, if that is even an appropriate interpretation. I even wonder if the money you spent on your boat/fuel, etc to show up counts.
Also, remember that you are subject to Cuban law when on their soil. That is standard international law. Should you find yourself in an accident, even if not your fault, or a bind of some kind, who are you going to reach out to for help? Will you call the "Special Interests section" which operates under the authority of the Swiss government, because we do not have an embassy there? First question from them.... what are you doing here?
This is just all too much for my risk tolerance.