> I thought Signal was open source, and the distributed binaries matched the source

This is sort of true. The source is published and you can build your own binary. But given that you can't distribute Signal outside of official stores and can't pin the version in those official stores (unless you turn off updates on your phone entirely), it's not actually practical to run an audited version, yet alone to make your own changes to the code.

> and that is was allowed to run your own servers. Are the servers even open source?

EDIT: apparently there is now (purported) server source available, not that that means much when there's no way to even know which code a given server is running, yet alone run a server with different code. They claim that their E2E encryption means control of their servers doesn't matter, but their protocol analyses doesn't actually think about what an attacker might be able to do at the server level, IME.

> Are there lirerature regarding the technical/conceptional bits Element/Matrix? What is the tradeoff there?

It uses either the same ratchet protocol as Signal or a very similar one. E2E for group chats is more complicated but I don't think you're giving up anything.

I started a high level doc a couple years ago to compare the major tradeoffs in most popular messengers here:

https://docs.google.com/spreadsheets/d/1-UlA4-tslROBDS9IqHal...

We also only assume the published Signal binaries match the published source code. Moxie and team have exclusive control of the signing keys and Moxie said he will fight any third parties like F-droid doing from-source signed binaries outside the Google/apple ecosystems in spite of the accountability and removed SPOF it would offer.

If you choose to use a non Google/Apple platform or a freedom-respecting architecture like RISC-V or OpenPOWER you don't get to be on the Signal network.

This eliminates me from being able to use Signal. Talked to moxie at length about this but in the end he repeatedly admits he has no problem cutting off the few to enforce his vision for the many. He also frequently implies he sees himself as the only entity worthy of running the world's communications systems.

He is a smart guy and means well, but he is naive. Benevolent dictators are always replaced by less benevolent ones eventually. There is nothing stopping what happened to WhatsApp happening to Signal. You also have to trust the pinky swear offered by the Signal Foundation that they won't dump the keys from their SGX enclaves using any of a myriad of design flaws, and that they, their ISP, datacenters, and any three letter orgs tapping them will all throw away all the TVP/IP level metadata that centrally flows to their systems.

With Matrix OTOH, if those that host a given set of binaries/servers go evil or we simply want control of our metadata for sensitive channels, we can just use one of the alternative independent clients or a fork, switch to our own server or one run in a country or by an entity we trust more. We also still will be able to reach our social graph, just like switching an email provider.

Democratic control is messy, but I will take it over a benevolent dictator any day.

As for documentation, matrix.org documents the API and design choices of Matrix extensively and they welcome people making alternative clients and bridges to other networks because they believe the only safe and sustainable network services are open ones.