My dad did a similar thing with a bunch of computers at his store. It made way more sense back when processors didn't clock down efficiently so there was such a thing as 'wasted/excess clock cycles' you could donate to a distributed computing project. Now though processors shut off cores, reduce their clock speed etc so there's a lot less spare processing power you can siphon off without increasing power draw.
People were doing this as a donation, not because they perceived it to be free.