Hi, I have spent some time skimming ancient archives and version control logs. It looks like you were the only person to ever work on the european portuguese translation of the manual page. Sorry to have gotten this wrong.
Do you really want to reassign copyright for your work to the Free Software Foundation? If not, I would suggest changing the wording to something like "(C) Copyright for the translation Américo Monteiro <a_monte...@gmx.com>, 2010 - 2023." If you want the FSF to be the copyright holder (which is not the case for the actual code in the adduser package), of course the header can stay as it is. I just want to understand your intentions. In any case, adding the usual "This file is distributed under the same license as the adduser package." would be appreciated for clarity. Greetings Marc