> IMHO, at some point, it's just about trust

Yes, but you are also literally going to multiply several billions numbers together and pray for a random outcome.

I don't know, maybe some middle ground would be feasible - like have the server-side part open-source, because that's the only part where anything harmful might be (and it's also fairly thin BTW).

But no matter what, the project needs to be profitable for me, sorry to say that, but let's be a bit realistic, you wouldn't work for free either.