My personal opinion fwiw is that approximately $50 per annum is a very minimal amount to pay for an excellent facility. Clearly he is not doing it to make an enormous profit and I would guess that Salvatore would be spending many hours of his own time gratis in maintaining the system. I personally think that we are lucky that we have fellow amateurs that are prepared to spend the time creating very useful tools for other to use and to do so at minimal or zero cost.
Just my 2c worth.
R