Can works that have fallen into the public domain be freely used?
Works in the public domain include works that have never been the subject of copyright protection, works whose term of copyright protection has expired, and works by the U.S. government. Works in the public domain may be freely copied and used. However, collections, translations and edited versions of works that contain or incorporate works in the public domain may be protected by copyright. The absence of a copyright notice does not mean the work is in the public domain and can be used freely.