terraform is OSS, unless you're using the hosted HCP version (workspaces? I think they're called), which, I've been using terraform heavily and at scale since v0.7 and I have never once thought I needed or would pay for something like that.
OpenTofu[0] is the OSS fork though.
[0]: https://github.com/opentofu/opentofu
Disclaimer: involved with OpenTofu
And thanks for contributing :)