Every municipality may levy and collect municipal taxes upon all taxable property within the limits of the municipality to provide for financial assistance to its development authority or a joint county and municipal development authority for the purpose of developing trade, commerce, industry, and employment opportunities. The tax levied for the purposes provided in this Code section shall not exceed three mills per dollar upon the assessed value of the property; provided, however, the authorization contained in this Code section to levy and collect such tax shall not be deemed to be exclusive and shall not prevent any municipality from exercising any additional power granted to it pursuant to any constitutional amendment, whether general or special, to levy any ad valorem tax for the purpose of providing financial assistance to any municipal or joint county and municipal development authority. The exceptions to the three mill per dollar tax limitation contained in the proviso of the preceding sentence shall not be construed so as to affect any action pending in court on February 20, 1984.