You do not have to register to use Surf. Surf is a tool for interacting with the Everscale blockchain and it neither requests nor collects any personal data.
When creating a new Surf profile, you need to read the Decentralization Policy and explicitly agree to follow it.
To read the Surf Decentralization Policy:
At the top of the home screen, tap the nut icon.
Tap Decentralization policy.