Merge branch 'authors-release-3-9' into 'master'

Authors release 3 9

See merge request !224

(cherry picked from commit 0415dd18)

ca6197cf Update AUTHORS.md
2a5da45e Update README.md gpl 2 to 3
b8110bb9 Update README.md change to newer link for gpl

Co-authored-by: Leon Keim <leon.keim@googlemail.com>