Documentation is a crucial point for every project, and the most
effective and traditional way to document a program is to write man
page. Here, the mdoc is used because it is simple.
Because the documentation is quite different from the project itself,
the man pages and others helpful files are distributed under a different
license. For this usage, the GNU All-Permissive License is adequate.
https://www.gnu.org/prep/maintain/html_node/License-Notices-for-Other-Files.html
man 7 groff_mdoc
Rodolphe Breard