[r3bl]

Not if they requested the contributors to sign the Contribution License Agreement (CLA) before accepting their changes.

Or, the other way (although I can't guarantee that this is true) would be to choose a compatible license with the one they were using before. Compatible license scenario basically means that the license changes are small enough so that they don't have to request from people to agree with the change.

[jevinskie]

And they do. I've seen their pull request bot block a merge many a time because of a lack of a signed CLA.