Err, looking at your hall.scm file, you have the fslib file added to your libraries twice.
Guix environment is not needed if you have all the requirements for building the package installed locally, but if you want to distribute your package it's good practise to ensure it builds in a clean environment (see also https:// guix.gnu.org/manual/en/html_node/Invoking-guix-environment.html for more information about Guix environments). The "COPYING" file is hardcoded as license file in Hall, to ensure compatibility with GNU standards: https://www.gnu.org/licenses/gpl-howto.en.html Hope this helps, Vale -Tim
