Speaking of nuclear options, need to get the providers to pledge/follow the fork, maybe via some kind of API incompatibility. Terraform is useless if the providers don't work with it and only the fork. Focus on disrupting the ecosystem.
This is the interesting part of all of this. The meat of Terraform is in its provider ecosystem. Anyone can make a new frontend (or even fork the existing one?), get rid of all the warts, add the missing encryption features gated under enterprise and have a much better tool.
Hashicorp left the provider frameworks under the original licenses, probably because they don't want to scare provider developers off. So for now both Terraform and a potential fork can continue sharing the same providers without issue.
Are they even able to unilaterally relicense third party providers?