Instead of making it free, if each family member paid $10/year for a FamilyLeaf account, that would (hopefully) allow the company to put forward a policy where users never need to worry about their privacy being violated for the sake of money.
I'm not saying that FamilyLeaf is doing this, but the need to monetize a free service drives companies to do strange things.If it was valuable enough to us, I could imagine paying a reasonable monthly rate (say, $25/mo or less) to host our entire family... but disposable income varies wildly in our (and I'm sure most) family.
In addition to that, we'll never charge any of our current users for what we are already offering them though in the future we may have additional features or plans that could be subscription based.