OpenTofu is a superset of Terraform. They maintain complete compatibility with Terraform while adding additional features on top of it. They have more dedicated developers on the project than Hashicorp does, and they are building out a fairly robust RFC process for the additional features.
I would not recommend using OpenTofu in production until they've had their first official release though. They currently have some alpha releases out that you can experiment with.
No, it's a superset of Terraform. The developers of OpenTofu have been adding every new feature in, and are committing to version parity. They've already got the new testing framework built out for example, as well as the changes to the S3 backend.
I would not recommend using OpenTofu in production until they've had their first official release though. They currently have some alpha releases out that you can experiment with.