It's not just a matter of being a no profit, it's also a matter of business incentives and target customers. Signal survives with donations and specifically targets the more privacy -conscious segment of the general population. They don't have a business model without the current setup, as the moment they advertise, sell data or do anything that violates the implicit contract with customers, their customer base disappears.

OpenAI on the other hand was "open" until it came up with a product, then it immediately stopped being so. But how many people from their customer base care about openness?

For signal also privacy is a core feature, for openAI being "open" was not.

I think the situation is very different, and while we should always check and never trust for free, we need to acknowledge the fundamental structural differences.