Texinfo files should contain sections that tell the readers that they have the right to copy and distribute the Texinfo file, the Info file, and the printed manual.
Also, if you are writing a manual about software, you should explain that the software is free and either include the GNU General Public License (GPL) or provide a reference to it. See section `Distribution' in The GNU Emacs Manual, for an example of the text that could be used in the software "Distribution", "General Public License", and "NO WARRANTY" sections of a document. See section Texinfo Copying Conditions, for an example of a brief explanation of how the copying conditions provide you with rights.