It's RentCast (rentcast.io) listings API and parcel boundaries come from state/county GIS services and Realie (realie.ai). Fair question on the rules: I'm not a broker or MLS member, so NAR/MLS rules don't bind me directly; I license the listings through RentCast's API under terms that allow displaying them, and how they source the data is on their side. I also left agent phone numbers and emails out of the downloads on purpose so the site can't be used to build contact lists. If anyone from an MLS sees a problem with a specific listing, I'd genuinely like to hear about it: [email protected]