It isn't at all. It is closed source powered by an American non-profit organization.
You can consider this organization as friendly.
They recurrently said, they would shut the gates if U.S. government/law wants them to store more than metdata (phone number+last activity date) they are storing.
@Valmond@SrMono Most popular out there and one of the easiest to set up / easiest to convince non-tech users to switch over to. Not the best... For me, that award would go to Matrix / Element.
Threema would be second (and should be first), but many will balk at the shocking fact that they dare to ask money to contribute to their development and operation costs...
What about SimpleX Chat? Comes without identifiers, is open source and not located in the US. Relay Servers are located in Germany, UK and Sweden and it's possible to host your own. Last audit was in 2024. No metadata is stored. Fundings are handled very transparently and presentated on the Website.
Not meaning to advertise it, just genuine interested in other peoples opinion.
In terms of security I would go Matrix, Threema, Signal.. in terms of usability I would say Signal, Threema, Matrix.
Threema also has a Business line which helps to cover the cost, but yea.. the price went up from 1€ to 5€. Back in the days I sponsored some licenses and spilled a bunch 1€ in the club like a rich man.
you can set up your own server for your own needs as far as I know, but you'll probably have to build your own version of the client to connect to it. there's no decentralisation.