Ponzi schemes offer payment based solely on recruiting. If you’re in a company where they tell you that all you have to do to make money is “Sign up a few friends, and get them to sign up a few friends” Then it’s most likely a pyramid scheme.
Referral Programs is about building a sales organization that sells a product. The ones who make the most money have the largest organizations, but it still involves selling a product. If there’s no product moving through the organization, then it’s not kosher.