What part of Signal isn't open source? Here is the server code https://github.com/signalapp/Signal-Server
Signal doesn't have a business model. It's not a business, it's a non-profit funded by a billionaire. It doesn't have ads, sell (or collect) data, etc.
One thing I appreciate about the Signal project is they don't make claims about security that aren't true.
Projects like bitmessage are great, but really need to prioritize UX if they want to be accessible outside of a tiny niche.