Of course you can make money - as long as you are honest about it.
- Usually they make money selling the installation, service, hosting or selling it in a double license with different graphics. There is no problem with that.
- Selling Metadata of users of an encrypted communication software without telling them while advertising it as exeptionally safe because of FLOSS is at least morally questionable
- And last not least the main point: they claim Signal to be FLOSS but it is not rebuildable as it relies on non-free parts. So lastly it is only claiming to be FLOSS.
- Saying: “This is FLOSS so use it” and in the same time making it only buildable with proprietary blobs + and talk bad about Forks which try to build it without these non-free blobs + closing the servers to these Forks + forcing/“encouraging” users to use Google Play is not upright.
Don’t understand me wrong - I am sure Signal is a well written beautiful piece of work. And as a user I would love to see it in F-Droid. BUT I don’t want to be sold on the way. There is something like a human right on data protection. Unluckily this is not treated very well these days. And that I even have to think about it regarding the use of FLOSS Software makes me really sad.