Every existing free public library shall be considered as if established under *this act, and the board of trustees and the legislative body of the governmental unit in which the library is located shall proceed forthwith to make such changes as may be necessary to effect compliance with the terms hereof; and every existing contract for library service shall continue in force and be subject to *this act until the contract be terminated or a library be established by the governmental unit for which the service was engaged. The provisions of *this act shall be construed as superseding the provisions of any municipal charter in conflict herewith.