What contract? You don't sign a contract when you create a Google account (which is basically what you need to create an API key with access to the free tier)
> 3.3 Restrictions.
> Customer will not, and will not allow third parties under its control to: ... (d) create multiple Applications, Accounts, or Projects to simulate or act as a single Application, Account, or Project (respectively) or otherwise access the Services in a manner intended to avoid incurring Fees or exceed usage limits or quotas;