> As far as I understand -- I'm not a lawyer -- changing a license requires that existing contributors are notified and agree to the change of licensing. Not t

> As far as I understand -- I'm not a lawyer -- changing a license requires that existing contributors are notified and agree to the change of licensing. Not the contributors, but the copyright holders. That's why usually projects require a CLA (Contributor License Agreement) to be signed, so they get the copyrights (or they get the rights to relicense the work).