License Vs. Contract is important because laws around them are different.

License	Contract
NO bargain for exchange.	Cannot Revoke other party's right.
There are stated requirements.	Else, breach of contract and pay damages.

Two states of license requirements

Comply	Not Comply
authority to undertake specified action under the license.	authority is not granted or revoked.
	if revoked its often without recourse (no remedy to reinstate license).

Note, this is NOT the same as saying that the software license is a contract.

So,

Can the software license be a contract?

Yes (not because you paid for software) but because of the Terms & Conditions incident to the software.

The End-user License Agreement (EULA) is license plus agreement. Some open-source softwares are also deemed contract.