To sum it up:
Signal - contains proprietairy libraries, namelely Google Maps integration, the rest of the code is FOSS.
Molly - Hardened Signal, compatible with contacts that use the Signal app.
Molly still contains proprietairy Google map integration, the rest of the code is FOSS.
Has extra features like TOR, Ram shredding, database encryption, etc.
Might have slightly delayed updates, not by much though.
Molly FOSS - Hardened Signal, compatible with contacts that use the Signal app.
Molly FOSS does NOT contain those Google map integration, the entire code is FOSS.
Has extra features like TOR, Ram shredding, database encryption, etc.
Might have slightly delayed updates, not by much though.
There is also a Molly FOSS version that uses unified push for push notifications.
Google and Apple push services can be read by the FBI, so Molly FOSS and Molly push are safe from that privacy invasion, you can also use GrapheneOS without Google services, this way all versions are safe.
https://www.reuters.com/technology/cybersecurity/governments-spying-apple-google-users-through-push-notifications-us-senator-2023-12-06/
IMO its best to use Molly FOSS is you don't care about Google maps integration.
Use Signal if you want bleeding edge updates, but no additional security features.
Please, correct me if I'm wrong.