In general, you do not need a user account. Most information is better updated by running an EDDN-compatible tool, and traffic reports may be submitted through CensusBot. You do not need an account to read any of the data on the site or to contribute to projects.
If you are sure you need an account, contact Ian Doncaster on the Census Discord to have it enabled once you have registered, or it won't do anything anyway.
Your email address will only be used if you forget your password and use the password reset features, never for anything else. If you aren't going to forget your password - or don't mind having to prod Ian if you do - you can safely use a fake one.