Their code is open source but you can't really do anything with that. You can't run your own server on the network, and they've previously stated they don't want third party implementations of clients.
Again, I don't trust promises anymore. Eventually they're going to need more money and that money will come with strings attached. If some org like Matrix would get bought people would just decouple themselves from their network. With Signal we can't do that because they are the only operator.
> Their code is open source but you can't really do anything with that. You can't run your own server on the network, and they've previously stated they don't want third party implementations of clients.
There are third-party forks and clients. Parts of the US government use one.