I thought I requested that https://github.com/WhisperSystems/Signal-Android was going to be made available on F-Droid too. Turns out there have been huge discussion on that topic. I hope much of the storm has passed and the time is now there to make this happen.
We added LibreSignal to the archive repo a while ago, but OWS made their standpoint clear: They will not tollerate 3rd party builds. So it got removed again. Eutopia still provides a fdroid compatible repo that serves it though.
This service is NOT independent from major players. Moxi, in a space of a year or two has turned from someone who was harrassed in airports by TSA into a receipient of many millions of $ from the US government plus lucrative contracts with Facebook. You don’t get that for nothing. Signal contains Google binaries; data goes through Google and their own servers. You can’t use Signal without having Google Services Framework, which renders any protection totally ineffective. Big players will get your outgoing messages before they are encrypted and incoming – after they have been decrypted. One of the real reasons Moxie has dropped SMS encryption, was that it actually worked without Google services, which was unacceptable to his paymasters.
Stay away from anything coming out of Open Whisper Systems. Use Silence (Textsecure fork) for encrypted SMS and Conversations, as a messenger.