How do they make money off it? I’ve used it to trace my family and never paid a dime. They offer free accounts.
There are a number of these genealogy services out there, and yes some of them are free, but you have to look for those.
Someone like Ancestry and a couple of others advertise all the time so a lot of folks sign up.
I am going to try your link. The Mormon Church is not trying to make money per se off their library but I imagine they are getting some.