Short answer. Only if that was agreed. In a free loan of a thing you get the use of the item, and its fruits still belong to the owner. But the Code expressly allows the two of you to agree that the borrower may use the fruits, and such a stipulation is valid.
What the law says
A stipulation that the bailee may make use of the fruits of the thing loaned is valid.
Civil Code, Article 1940 — Use of Fruits. Read the full provision →
What 'fruits' means, and who gets them by default
Fruits are what a thing produces without ceasing to be itself: the harvest of a field, the offspring of livestock, the rent a house earns, the interest a deposit yields. In a free loan of a thing — commodatum, where you borrow an item, use it, and give that same item back at no charge — what you are given is the use of the thing. The fruits are not part of that. They accrue to the owner, because ownership of the thing was never transferred to you. So a borrower who harvests and sells a crop, or pockets rent from a lent property, is taking something that was not included in the loan.
The agreement that changes this
The article settles a question that could otherwise be argued endlessly: whether letting the borrower take the fruits is inconsistent with a loan that is supposed to be free. It is not. The owner is free to be generous twice over — lending the thing and throwing in what it produces — and an agreement to that effect holds. Nothing in the Code requires such a stipulation to be in any particular form, but the practical advice is the opposite of that. Put it in writing and say which fruits are covered, because a dispute a year later is a dispute about what two people remember agreeing to.
Where the arrangement stops being a free loan
The permission is meant to be an extra on top of a gratuitous loan, not the heart of the bargain. Where the real deal is that you enjoy the produce and the owner receives money, a share of the crop, or some other return, you no longer have a free loan at all — you have a paid arrangement, and the rules on leases or on usufruct apply to it, along with a different set of obligations for both sides. What you call the document does not decide this. What decides it is whether the owner is getting something back.
What the borrower still owes
Taking the fruits does not change the rest of the relationship. The thing itself remains the owner's and must be returned, in the same identity and condition, when the period or the purpose ends. You continue to bear the ordinary expenses of using and preserving it, and you answer for damage caused by your own fault or by using it for something other than what was agreed. Nor does the permission make you an owner of anything beyond the fruits actually gathered while it was in force. Once the loan ends, whatever the thing produces afterwards belongs to the owner again.