Upon expiry of the term of copyright protection, works are released into the public domain, where they may be freely used. They may be copied completely, put online, exploited commercially, etc. According to prevailing opinion in the legal doctrine, the moral right of the author is also lost when the term of protection expires. In specific terms, this means that you may publish a third-party work if it is in the public domain, as long as the author has not published their work themselves. You may also publish a third-party work under your own name. However, good scientific practice sets very clear boundaries here. For example, anyone who submits a dissertation in the public domain under their own name is committing plagarism.
Furthermore, "copy fraud" is considered to be the illegal presumption of copyright, in which someone publishes a third-party work in the public domain under their own name, and in doing so suggests that the work is still protected by copyright or protected by copyright once more (i.e. puts a work in the public domain online with a Creative Commons licence, which forbids commercial use of the work). Although someone may principally publish a work that is in the public domain under their own name, a work whose copyright protection has expired on one occasion cannot be endowed with copyright protection once more in any circumstances, which means no limitation of any kind of use of the work in question is permitted.