"Porcupine" is the nickname for Free Staters.
In answer to your question "what do they do" yes you're right the FSP as an organization does not back candidates or affiliate with parties or what not. Its sole official purpose is to persuade 20,000 liberty minded individuals to move to NH and facilitate the move. What happens inside NH is not really the FSP's call.
However individual free staters led by those already in NH have formed a PAC inside the state. It's called the New Hampshire Liberty Alliance. I kinda like the way that sounds, reminds me of the Rebel Alliance from Star Wars :) However they report no X-Wings in operation currrently.
The Alliance site is
http://nhliberty.org But the most interesting day to day action is still at www.forum.freestateproject.org
Practically anything goes there and individual FSP members and local groups have all kinds of things going on.