Since we're talking alternatives, there's also Matrix (https://matrix.org/ https://matrix.org/) which: - Is an open protocol - Has Apache 2.0 licensed server

Since we're talking alternatives, there's also Matrix (https://matrix.org/ https://matrix.org/) which: - Is an open protocol - Has Apache 2.0 licensed server and client implementations for most platforms - Has server federation, so you can run your own and talk to anyone on any other Riot server - Has (optional but I believe enabled by default now) full end-to-end encryption - Has full multi-device support - Doesn't require nonsense phone number signup - Has bridges that connect other protocols, like IRC, to Riot - Supports useful things like voice, video and attachments It beats Signal hands down in my opinion. Not affiliated with the project, just run my own server and use it constantly.