Z:gnu-www-ja-gpl-2.0-faq--7e2fa2-=3Ca href=3D"=23Consider" name=3D"TOCC/en

Consider this situation: 1. X releases V1 of a project under the GPL. 2. Y contributes to the development of V2 with changes and new code based on V1. 3. X wants to convert V2 to a non-GPL license. Does X need Y's permission?