At least BlueSky is built on a technology based on open standard protocol and is decentralized. Kind of similar to the goals of Fediverse / Mastodon. So I assume someone else can just create a server and join the network of BlueSky? I don’t know if this is possible. But in reality at the moment its controlled by only one big company.

My hope is that they will one day cooperate with Fediverse, so it becomes read from and write to relationship.