Z:gnu-www-ja-gpl-faq--ea1e39-A file containing just a licen/en

A file containing just a license, without a statement that certain other files are covered by that license, resembles a file containing just a subroutine which is never called from anywhere else. The resemblance is not perfect: lawyers and courts might apply common sense and conclude that you must have put the copy of the GNU GPL there because you wanted to license the code that way. But why leave any uncertainty?