No, that doesn't work. You can't retroactively change a license like that. What could happen is that future versions get licensed differently (if either all con

No, that doesn't work. You can't retroactively change a license like that. What could happen is that future versions get licensed differently (if either all contributors agree, the project used a CLA or is permissively licensed). Either way however then you could either stop using it or fork the project.