Notwithstanding any general or public law or rule to the contrary, income from investments in the capital development fund may be applied to capital purposes and shall not become part of the general fund of the state to the extent necessary to exempt (in whole or in part) the interest paid on such bonds or notes from federal taxation, to preserve and maintain any federal tax credits associated with such bonds or notes, or to preserve or maintain any refundable tax credits paid or to be paid to the state with regard to such bonds or notes.