Explanation of Article 507
The article clarified that the default in a deposit contract is that it is gratuitous; the depository does not receive a fee for keeping the deposit. However, it is permissible to agree that it will be for a fee, whether the agreement is explicit or implicit. An implicit agreement can be when custom dictates that certain types of deposits are kept for a fee, or when the depository is someone who keeps deposits professionally, which is considered an implicit agreement on the fee; the depository is entitled to a fee for keeping the deposit, even if it is not explicitly stated.
Related To
Article 507
A depositary shall receive no fee for safekeeping the deposited property, unless agreed otherwise.