The competitive advantage to "X is a protocol versus a license" is it's inherent proclivity to being bootstrapped. It's no different than Bitcoin spawning a million nodes from a single white paper.

The big worry is how do you maintain that early adopter culture as the service scales. Some will adopt invitation-only gatekeeping. Others an onboarding process that emphasizes customer development.

Mastodon makes its culture explicit up front and in its design. And it seems to be working.