Is the transaction considered usurious if the capital is guaranteed to the partner and the duration of the partnership is specified, knowing that it is a partnership in a transport bus and a sharing of profits? Does this fall under the category of Mudarabah?

This transaction combines a company and a Mudarabah (profit-sharing partnership), and it is permissible. The profit is to be shared between the partners as they agree, and the loss is according to the capital contributed by each. It is permissible to set a specific duration for the partnership, but it is not permissible to stipulate a guarantee of the capital. The loss will be borne by the partners according to each one's capital.

The correct approach in this transaction is that the condition of guaranteeing the capital is void, while the contract itself remains valid. The correction is made by agreeing on a specific duration for the partnership. Upon its expiration, there will be a non-binding promise to purchase the partner's share at the market price on the day of sale, not at its original price.