Lemmy is AGPL. From what I understand, that means anyone running Lemmy (or a fork of Lemmy) needs to make their source code public, even if their code changes are strictly to support their own network infrastructure.

it really doesn’t matter though, as a corporation only needs to implement an interface to Lemmy via ActivityPub protocols; in other words it they could write a completely closed-source backend to use for profit and as long as it can poop out the correct data structures over ActivityPub to allow Lemmy instances to understand it, it will work.

This already happens as we can see and subscribe to kbin magazines, and Mastodon users can be @'d and IIRC can reply to comments via Hoot (or whatever they call it). Kinda wild, but it also leaves the door open to literally whoever.

I think the real interesting question is will a large corporate player be able to maintain a captive userbase? None of the doomsday scenarios play out in their favor unless they can capture users and communities - because then the usefulness of the whole thing rides on their server being available. At that point it’s reddit with more steps - they can do what they want.