[smcphile]

> Also technically I guess (IANAL) you might have to prove that you obtained the source code prior to the license change.

I don't see why. If some code is made available under an MIT license and then the copyright owner switches to a new license, nothing stops others from continuing to use the original code under the original license.

Of course to do this you would have to know the code exists, but you could learn about its existence after the license change from someone other than the copyright owner.