Is money taken for trade, with the condition of half the profit and a guarantee of the capital, considered usury (riba)?

If a condition is imposed on the recipient of the money to guarantee it and bear the loss, and that the owner's capital will be returned to him, then this is a فاسدة (invalid) Mudarabah (definition), and its reality is a loan with interest, not a legitimate investment. Loss in Mudarabah funds is borne by the owner of the capital, and the Mudarib (investing partner) is not responsible for it unless he transgresses or is negligent. The Mudarib is a trustee and an agent for the owner of the capital, and a partner in profit. If the Mudarabah contract becomes invalid due to the agent guaranteeing the capital, then he is entitled to a fair wage for his work.