How so? I believe every single line of everything is open source, aside from their server-side Discover feed algo. But in any case, the question is about the app, which is 100% MIT licensed open source code.
Real "open source" would for me even imply that all data is freely accessible but this stops way, way before and should not be called open in almost any sense.
Just a VC PR play.
Real open source is any software with a license that obey the four freedoms..
1 - freedom to view the source 2 - freedom to use 3 - freedom to modify 4 - freedom to distribute your modified version
Bluesky use the MIT license that does comply with the freedoms above, so it is real open source..
Also, it use a open protocol as well.. so nothing is stopping you from deploying your own instance [1] and use their app to connect to it.. then you will have all your data freely accessible as you want..
You may believe that it is not "open/publicly-available enough", and that is a totally fine opinion to have. But if you say "open source" on HN, people will understand something very different.