I never noticed the JFF box.
Anyway, we've become trained to mistrust anything that's offered for free on the Internet. You pay for "free" items or free offers in several different ways...Taking endless surveys at the end of which you're required to make a purchase that often supercedes the cost of the free item, or provides no obvious way to actually get the free item; signing up for "free trials" that require credit card information, and if you don't cancel your free trial when the fine print tells you, you get screwed with a whopping bill for Japanese anime, Dried Fruit of the Month, or a lifetime subscription to learning a Malayo-Polynesian language online, essentially committing to a subscription for something that no one wants in order to keep the free item that often equals or again surpasses the cost of the free item, such as looking up a person's criminal history online or finding out how much people earn who work on oil rigs in Nebraska and other states.
The kicker is that we then find our mailboxes filled with offers from the original site offering something for free, as well as from Publishers' Clearing House, low-cost life insurance, Geico, Secret Shoppers, free credit scores and everyone who offers coupons for pet-store reptiles. As you suggested in your comments, LB, we've effectively learned to avoid free offers. Typically a waste of time.
The JFF conundrum is a branch of Dissonance Theory and a tried and true marketing strategy. When the cost of buying a particular item or service is experienced as too low or too high, it triggers emotional discomfort when we debate with ourselves over whether or not to make the purchase. If something is genuinely "free," then it simply can't be worth very much and will probably be disappointing. However, if the same item costs $0.99 (or a relatively low price), then I've most certainly gotten a deal. Thus the proliferation of "Dollar Stores." This all changes when the price is too high, when our thoughts and experience tell us that we're paying too much for what we expect to get. At higher prices, the strategy is to make the consumer believe that he or she needs the product offered, over and over again, and that they'd be missing out on some vague sense of satisfaction were they to go cheaper, that there is a personal bond forged between the consumer and the product. (I love Apple products and was a registered Apple software developer for a few years around the turn of the century for specific projects, but they've certainly cashed in on this strategy, approaching a trillion dollars in valuation.)
Another variation of dissonance theory is getting paid to do a particular task. If I'm offered ten bucks to make a simple delivery, I'm more likely to do it than were I offered a hundred bucks. Believe it or not, being overpaid for providing services also triggers emotional discomfort in terms of people's values (despite the fact that many people would accept the "extra" payment). Think about the contradictory thoughts and feelings that accompany being offered a reward for doing what is "right"...returning a lost wallet. Though I may believe that I should be rewarded for my work, being overpaid for what I do can be unsettling, often accompanied by a sense that I will be indebted to the person who pays me or that there will be an expectation that I have to do things that I may not want to do in order to get paid in the future. Or, simply, that I wouldn't overpay someone else to do the same task, since doing so would breach my value system, and it therefore causes discomfort for me.
There's lots more, and I'm not explaining this as well as I might, but how and why we spend our money, and how and why we accept it from others, is rife with internal debate. In the original example, if recovery sites offered a lifetime memberships at an average cost of say, $4.99, I might be put off by SR were it offered for a $0.99 or for free, whereas $3.99 might be worth it to me to give it a try.
In the end, it's much better to offer membership for sites that offer support without any cost, freeing the user to feel that whatever they get out of the experience was given freely.