YOU DO NOT NEED A SALTWATER LICENSE TO FISH IN MASSACHUSETTS IN 2010.
Either a Federal registry card or a RI/CT license will provide proof of registration.
You WILL need a valid saltwater license to fish in Massachusetts beginning January 1, 2011. This can be a Massachusetts license, OR a RESIDENT license from a state that grants reciprocity to Massachusetts residents. As of now, the states that grant such reciprocity are NH, RI and CT. The Federal registry card alone WILL NOT allow you to fish in Massachusetts next year.
I hope this makes it clear. There is way too much confusion and wrong information being bandied about.