But my understanding is that the copyright holders have the right to change the license.
To clarify, the copyright holders have the right to relicense their work under a new license. This does not mean that old versions cease to be licensed under the old license -- works can be simultaneously available under several licenses, in which case people can decide which license to take advantage of.
To clarify, the copyright holders have the right to relicense their work under a new license. This does not mean that old versions cease to be licensed under the old license -- works can be simultaneously available under several licenses, in which case people can decide which license to take advantage of.