The more I look into this, the shadier it seems.
They're selling at a whooping $79/month, a single php script that does not even check any sort of authentication or API key, and only does a dumb lookup against a GeoIP database : https://gdpr-shield.io/check.php
And this is called by this tiny javascript script https://code.gdpr-shield.io/script.js that just.. displays an overlay div when you're in the EU. Smells like scam when you're willing to sell a whole product that can be coded in 20 minutes for up to $1000 a year.