Indebtedness incurred under this chapter and evidences of indebtedness issued in connection with the indebtedness shall be deemed to constitute a proper public purpose and the evidences of indebtedness issued, their transfer and the income from them, including any profits made on the sale of the evidences of indebtedness, shall at all times be exempt from taxation within the State.   [PL 1987, c. 735, §14 (NEW).]