Now, if you are like me, you hear the words “open source” and “decentralized” and then the word “CEO” and think, wait, why does the decentralized open standard have a CEO? The whole point is that no single person or company is in charge, right? Well, welcome to the wild world of open-source governance. It’s a riot, my friends. You’re going to hear me and Eugen say the phrase “benevolent dictator for life” in dead seriousness because that’s how a lot of these projects are run.
Eugen Rochko is CEO of Mastodon gGmbH which is the company which develops the Mastodon software. It isn't the software itself; that's open source and could be forked and developed by anyone. Nor is it any of the instances which can be operated by anyone who wants to and they don't even have to use Mastodon's code to do so.
I could set up a company to run an instance and call myself CEO if I wanted, it would only mean something to users on my instance, I guess.
The overlapping names are, probably unintentionally, slightly confusing.