They didn&#x27;t need to contact the contributors because of that &quot;or later&quot; clause. The license explicitly lets anyone relicense to GPLv3 without asking anybody first.<p>Linux&#x27;s license doesn&#x27;t have that clause, so you&#x27;re not automatically allowed to relicense. Switching to GPLv3 would require the copyright holders to explicitly do so. Since Linux doesn&#x27;t require contributors to assign copyright to some central organization, &quot;the copyright holders&quot; means all contributors, past and present.