Section 17. No bond, note or other evidence of indebtedness executed or obligation or liability incurred by an operating agency shall be a debt or charge against the commonwealth or any political subdivision thereof other than such agency. Nothing in this chapter shall be construed to obligate the commonwealth, or any political subdivision thereof other than the applicable operating agency, or to pledge its credit, to any payment whatsoever to any operating agency or to any creditor or bondholder thereof, nor shall anything therein contained be construed as granting to any operating agency any exemption from taxation except as expressly provided therein or to render the commonwealth, or any political subdivision other than such agency liable for any indebtedness or liability incurred, acts done, or any omissions or failures to act, of any such agency.