About the give-away-for-free aspect I was also wondering. Do they maybe configure their dns servers as default upstream and hope many people keep the defaults? DNS is one of the best technologies to do data mining and sell the data. I guess it's also why all those easy to remember dns servers like 8.8.8.8 and 1.1.1.1 exist. Google and Cloudflare for sure don't do it just to be nice.
Disclaimer: adguard claims not to sell any customer data.
Disclaimer: adguard claims not to sell any customer data.