It seems like this is macOS only? It's not really explicitly spelt out - you just have to work it out through context clues (screenshots showing macOS borders, "macOS Ventura is 'recommended'").

I can definitely see someone not realizing before getting to the payment page - probably needs to be an explicit list of supported OSes somewhere.

Edit: just noticed the expandable 'what platforms does Taim support' at the bottom. That should be bigger, and not buried with the rest of the FAQ stuff imho.