"[...] For example, if you distribute copies of such a program, whether gratis or for a fee, you must give the recipients all the rights that you have. You must make sure that they, too, receive or can get the source code. And you must show them these terms so they know their rights.[...]"
Quelle: http://www.gnu.org/licenses/gpl.html
Das dürfte ja wohl alle Fragen ausräumen.