Using GitHub Actions to deploy your Terraform code (you becoming the third party) is competitive with HashiCorp's products. There is no delineation about commercialization.
HashiCorp probably won't come after you, but to me it shows this wasn't really thought through or it's maliciously ambiguous.
In every case, the same people made the same mistakes with other tools. A common trait was that they [incorrectly] thought they were rock star developers and boring details like how their code actually runs were beneath them so they wasted huge amounts of time on deep module structures (or with CDK, elaborate TypeScript hierarchies) but resisted learning how the AWS resources they used actually worked.
Much easier to hand them Terraform and reject anything with local-exec provisioner, the official worst piece of terraform.
Though of course there's also teams that run ansible from it with lots of implicit settings, making it a pain to move from dev machines to CI.