What does he mean there is only one "Bluesky server" ?
You can already run your own Personal data server (for your data), Relay (to aggregate all feeds), AppView (that holds a view of the data), or client (that talks to the AppView).
You can already run your own Personal data server (for your data), Relay (to aggregate all feeds), AppView (that holds a view of the data), or client (that talks to the AppView).
The AppView - controls the way you can search posts - has the ability to show or hide posts from everyone using that AV - has per-user data such as notifications, last skeet seen etc - is a CDN for media, and as such can filter there - is where the algorithms of what posts to show are implemented
In other words, someone who controls the AppView holds a lot of power in the AT Protocol world.
At the moment, it seems that Bluesky are doing a great job with their AppView, and they've rather magnificently scaled with the extreme load increases in the last months. However, for someone like Doctorow who wants independence from being on someone else's platform, there has to be a viable alternative AppView, or at the very least a documented process for how to host it.
However, it's my personal belief that it's only a matter of time until people do this. I don't know how practical it will be (and what level of resources would be needed to divulge if Bluesky go bad compared to a Mastodon server), but it seems like this is a priority for them, and everything else in the stack has been made easy to self host (see https://alice.bsky.sh/post/3laega7icmi2q).
If that is true then that probably goes a long way in addressing the concern Doctrow and others have with Bluesky.
edit: According to one article[1] PDS isn't really full federation like what mastodon has. Right now you can only host your own account in your PDS (But they plan to gradually increase that limit to 10, and then more later)[2]. But it's certainly a good start. Not sure if Bluesky will have the capability to block you from reaching your own followers though (say if they ban or suspend your account).
[1] https://www.theverge.com/2024/2/6/24062837/bluesky-drops-inv...
What you lose (at least last I checked) are action notifications based on your forwarded handle(s). This mostly doesn't matter, though in my case I have one mildly-viral toot which occasionally gets rediscovered. Missing out on the notifications storm there is mostly feature rather than bug.
For the curious: <https://mastodon.cloud/@dredmorbius/102376653178100454>