https://developers.facebook.com/docs/internet-org
> Free Basics by Facebook provides free access to basic internet services to a billion people all over the world. Your service can be part of it.
> In order to make your website display properly within the Free Basics Platform and be accessible to people on all types of phones and data plans, your mobile website(s) must meet certain technical conditions created by the Free Basics proxy. [...]
Granted, I don't know how difficult it is to get a service included, but I've seen them mention a number of times that they intend enrollment to be open to anyone. The participation page seems focused primarily on technical issues like how easy the site is to proxy and cache, in order to serve a bandwidth-light version.