Their current CLA provides for a full copyright license grant: https://www.hashicorp.com/cla Assuming that's not new (and I have no reason to believe it is) then contributors were already signing away their right to be choosy in that regard; Hashicorp can already relicense any previous contribution, which is why this change is even possibly in the first place.

I agree that it might cause some bad vibes, but it's no different for these in-flight PRs than it is for all of the historical ones that were already merged.