No, not tapatalk. It doesn't need an app. You just open the chat on the psychforum site. That's what I do, anyway? I've never had to pay anything.
Click on the chat tab on the psychforum site... it may prompt you to sign in, but think all you do is use your forum sign in. And then it should open straight away, There shouldn't be any woman wanting a phone number and no payment is required!