The short answer is "Yes". Anyone who wishes to participate in an SBPS Contest or create their own SBPS Contest will essentially have an SBPS User Account.
However, this isn't anything complicated, and has absolutely no cost associated with it.
The "SBPS User Account" is simply a placeholder for you, that holds your email address and name. That's it.
The purpose of this User Account is to protect you and your identity, against anyone using your email address on our site without your permission or knowledge. If you were to return to the site next week or next year and try to reserve additional squares with your email address, the site simply says "Welcome back! Now prove you're you."
Additionally, the User Account protects the contest commissioners against random people entering other people's information, such that they are more confident that the email addresses given to them are indeed the people who they say they are.
You'll get important box confirmations when you reserve a square, which is another reason why it's crucial for the system to simply have at least your email address.
So in conclusion, while it is technically a "user account", it's nothing more than just a unique pairing of your email address and name in our system for pretty obvious security and confirmation usage.