Z:gnu-www-ja-gpl-faq--730e52-If a tighter requirement in a/en

If a tighter requirement in a new version of the GPL need not be obeyed for existing software, how is it useful? Once GPL version 4 is available, the developers of most GPL-covered programs will release subsequent versions of their programs specifying &ldquo;Version 4 of the GPL or any later version&rdquo;. Then users will have to follow the tighter requirements in GPL version 4, for subsequent versions of the program.