As per http://git.savannah.gnu.org/cgit/groff.git/tree/COPYING and e.g. http://git.savannah.gnu.org/cgit/groff.git/tree/src/roff/groff/groff.cpp LICENSE is GPL-3+ since 2009 http://git.savannah.gnu.org/cgit/groff.git/commit/COPYING?id=0ba9ac513f520a1a82bc2392340c2b9f65756909. Some stray files like http://git.savannah.gnu.org/cgit/groff.git/tree/src/libs/libgroff/localcharset.c are GPL-2+ Reproducible: Always
Also the tarball contains LGPL-2.1+-code in lib/.