What does Freemius do?

Freemius allows a WordPress plugin developer to distribute a premium plugin on their own website. The service offers the ability to take subscription payments, offer discounts, manage users, and set upsells and cross sells. You can distribute your primary plugin, as well as offer add-ons. It's a fully integrated system that requires some developer knowledge, but overall it is user friendly. There are web hooks for synching to third party services like MailChimp and HelpScout with more on the way.