We lied (sort of): the ticket isn't entirely "free" (nothing ever is!);
You have to submit a one paragraph review of a past s|n gig by email.
(Remember to say which gig you want a ticket/name-on-the-door for).
OTOH you don't "win" in the traditional sense either. 
You simply get a ticket automatically by being a supporter of s|n.
You get a ticket and we get a micro review for these Web pages. Win-win.