I thought this was slightly funny.
Mark Zuckerberg is known these days for wearing t-shirts with Latin phrases on them, especially ones where he compares himself to Julius Caesar.
Bluesky made a shirt in the same style, but theirs says “a world without Caesars” in Latin.
There are significant differences in account portability. ActivityPub allows you to transfer your followers to a new server, but not your content.
Nothing in ActivityPub says you can’t move your content from one platform to another. It’s just that Mastodon does not have this feature at the moment.
Meanwhile, I’m not sure whether Bluesky has this feature or not, but it’s somewhat irrelevant considering the fact that there are no other platforms to move your content to. The only thing I’ve actually seen from this is that you can use an URL as your username in the front-end, though it just points towards the same DID in the backend. I struggle to see what the great achievement here is.
If this was the reasoning behind Bluesky, they could have developed a platform running on AP supporting the transfer of content between instances, and it would have been a whole lot easier than developing a whole new protocol.
Your content in ActivityPub is linked to the home instance. So for example I can’t move this post from lemmy.world to another server. I could copy/paste the content into a new post on another server, but it would be a broken piece of our conversation with no context or replies.
Also, hosting a ATProto self-instance is not as expensive as you suggest. This person did it for $150/month.
Fair - you could host a copy or a link (or a sort of combination between the two, I guess), but it wouldn’t transfer the ownership of the original post. I’m still not sure this is such a pressing feature that I accept it as the actual raison d’etre of AT proto, especially considering how it very much exists there only in theory at best. But it is interesting technology, and something they could maybe have worked with ActivityPub to try to achieve.
I’m glad to hear that maybe Bluesky is more decentralized than I suspect, but Bluesky engineer whose blog post you linked still links to his bluesky account on bsky.social. If running a separate instance is achievable, I would love to see people actually do it.
My understanding is that running most of BlueSky is possible on small to moderate hardware. However, running all of BlueSky requires basically cloning 100% of all the content on BlueSky (which, as of Nov 2024, was ~5 TB).
So, like, yes, one can run part of BlueSky or a clone of BlueSky which has none of the main instance’s user’s content without much trouble, but actually running an entire BlueSky stack is eventually going to become cost prohibitive.
I found this write-up to be enlightening on the subject.