For me personally an ad is when I’m being sold something. I can’t be sold something that is free and open. So someone showcasing their paid (but self hosted) service is an ad. Someone telling me about their (open) project is not.

And when someone wants to use either and asks for help, is also (obviously) not an ad. Unless we see a flood of accounts posting trivial questions about a paid service to draw attention to it, but I kinda doubt it.