Apple has set up a FAQ within iTunes Connect for Family Sharing in iOS 8, and it reveals more details about the upcoming feature. The feature lets up to six family members share iTunes, Books, and App Store content through the credit card of one adult with an Apple ID, referred to as “the family organizer” in the FAQ. The FAQ notes that if a family member leaves the group, “their purchases — including any purchases made while part of the Family — will no longer be available to the remaining family members, and vice versa.”
It’s also notable that in-app purchases cannot be shared with family members — apps that only allow access of most content through an in-app purchase will be far less useful for those accessing the app through Family Sharing. Further details can be seen in the included screenshot.