Hello,

Ninja Cookie is free, doesn’t display 3rd party ads, doesn’t collect or sell data. We cannot make a living out of Ninja Cookie’s freeness. To fund the development, we offer a premium version. For more openness and flexibility, we have opted for a “Pay What You Want” fee.
To promote the premium features, Ninja Cookie displays a single message at day+0, day+7, and day+30 after installation. This way, we hope we are not too intrusive. If more messages are displayed, it's because of a bug. We would be really happy to have more information to fix it through our contact form https://ninja-cookie.com/contact/

Have a good day!