The CNCF has made exceptions on their license policy before, specifically for MPL based software. It'll probably be easier for OpenTF to go through that process than to relicense (which is likely not even possible for anyone other than Hashicorp).
- https://github.com/cncf/foundation/tree/main/license-excepti...
- https://github.com/cncf/foundation/blob/main/license-excepti...