Z:gnu-www-ja-gpl-faq--3cf2b0-Section 2 says that modified v/en

Section 2 says that modified versions you distribute must be licensed to all third parties under the GPL. &ldquo;All third parties&rdquo; means absolutely everyone&mdash;but this does not require you to do anything physically for them. It only means they have a license from you, under the GPL, for your version.