probably true but Signal is open-source. But we need to keep an eye on them.
NSA : Thanks for sponsoring open source tools
Discussion
Has a central server. Is all that also open sourced ?
I think it's fair to say that one of the founding premises of Signal is that you can't trust the server that operates the messaging service.
So the answer is that you design your service in such a way that it doesn't matter, for privacy and security purposes, what server it's running on. Once you've done that, you have the freedom to just use whatever's the most reliable and/or affordable.