Trying to figure this out as in the recent threads a few people said that Bluesky was federated, but it didn't seem to actually be the case.
https://bsky.social/about/blog/02-22-2024-open-social-web in February announced that Bluesky would allow federated servers
The Bluesky documentation on the topic isn't very clear. They mention Bluesky.social a lot, as if it's supposed to be the one central server other PDS need to federate with:
Bluesky runs many PDSs. Each PDS runs as a completely separate service in the network with its own identity. They federate with the rest of the network in the exact same manner that a non-Bluesky PDS would. These PDSs have hostnames such as morel.us-east.host.bsky.network.
However, the user-facing concept for Bluesky's "PDS Service" is simply bsky.social. This is reflected in the provided subdomain that users on a Bluesky PDS have access to (i.e. their default handle suffix), as well as the hostname that they may provide at login in order to route their login request to the correct service. A user should not be expected to understand or remember the specific host that their account is on.
To enable this, we introduced a PDS Entryway service. This service is used to orchestrate account management across Bluesky PDSs and to provide an interface for interacting with bsky.social accounts.
https://docs.bsky.app/docs/advanced-guides/entryway#account-management
Self-hosting a Bluesky PDS means running your own Personal Data Server that is capable of federating with the wider Bluesky social network.
https://github.com/bluesky-social/pds?tab=readme-ov-file#what-is-the-current-status-of-federation
The custom domain name is still something else, and does not seem to require a PDS: https://bsky.social/about/blog/4-28-2023-domain-handle-tutorial
So, to come back to the title question, do people know of an example of PDS that can be used to access Bluesky without being on the main server?
@Blaze AT (Bluesky's protocol) is a little bit different then activity pub. There's two types of servers, a PDS and a relay. A PDS is basically a git repository of all your posts/interactions, it's super lightweight and doesn't do anything but host them and provide it to any server that asks for it. The PDS basically does the profile hosting portion of a Mastodon server, and is very similar to a Nostr relay if you're familiar with that.
A relay accesses data across a bunch of PDSs and provides it as one big network to the relay's users. It's basically the equivalent of the federated portion of what a Mastodon server does. It's also doing what a Nostr client does (although Nostr does that on the user's device) if you're familiar with that.
Any relay can pull data from any PDS, so theoretically it's very decentralized since anybody could host either a PDS and/or Relay. Bluesky was opened up very recently though, so there's not many non-Bluesky-hosted PDSs on the network yet and most are small and experimental. There's also no relays other than Bluesky that I'm aware of, although it's only been open for ~6 months so I expect that'd change soon.
Thanks for clarifying!