His grand vision remains to leave Mastodon users in control of the social network, making their own decisions about what content is allowed or what appears in their timelines.
I don’t use Mastadon cause I don’t care for micro-blogging, but nevertheless, I like this.
The computer program called Mastodon was (and still is for now) completely controlled by Eugen Rochko. In the future it will be controlled by a non-profit.
See this and this for more info.
In as much as FOSS can be forked, it’s not really completely controlled (and there are a number of active mastodon forks that federate fine with standard mastodon servers)
Of course you can fork it, but you can’t call it Mastodon. That’s trademarked. Just like how you can fork Firefox but have to call it Waterfox or Iceweasel or Librewolf.
The confusion here is between Mastodon the company and Mastodon the software and instances of the running software. Eugen Rochko owns the first two. He also owns the instances mastodon.social and mastodon.online. Everything else is outside of his control.