Determining commodatum, mutuum

Articles 1933 and 1953 of the Civil Code provide the guideposts that determine if a contractual relation is either commodatum or mutuum:

Art. 1933. By the contract of loan, one of the parties delivers to another, either something not consumable so that the latter may use the same for a certain time and return it, in which case the contract is called a commodatum; or money or other consumable thing, upon the condition that the same amount of the same kind and quality shall be paid, in which case the contract is simply called a loan or mutuum.

Commodatum is essentially gratuitous.

Simple loan may be gratuitous or with a stipulation to pay interest.

In commodatum the bailor retains the ownership of the thing loaned, while in simple loan, ownership passes to the borrower.
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Art. 1953. A person who receives a loan of money or any other fungible thing acquires the ownership thereof, and is bound to pay to the creditor an equal amount of the same kind and quality. (Emphasis supplied)