It works when it's just software that you can support on your own later (open source). It doesn't work when it's SaaS.

It is that. It's free unless you find it so compelling you want to give the creators money you can. I'm sure the only thing stopping that from happening "back in your times" was that setting up a payment processor and accepting payments didn't take 15 mins. At no point do they say you can't use it if you don't pay