A license isn't a contract that binds the licensee, it's a contract that only binds the rightsholder. Since you, the licensee, are not relinquishing any rights in the contract, there's no need for you to agree to anything. The only rights being relinquished are the rightsholder's right to pursue legal retribution for some uses of their work that would otherwise be violations of copyright.

You dont have to call it a contract, but it is a legal document in which one or more parties legally bind themselves, which seems like an adequate definition of a contract to me, and has more etymological fidelity to the word "contract" than other possible definitions that would exclude licenses. A contract is a legal instrument by which the breadth of your rights contract — as in become smaller.