I never understood this sentiment. Hashicorp offers Sentinel for free [1], publicly. The documentation is also open [2]. There's also open rulesets for CIS benchmarks [3] (minimal but demonstrates what Sentinel can do), and a ton of public drop-in rules for several clouds [4]. There's helpers [5,6] for common use cases, supports custom integrations [7] and it can be run in CI [8].

[1]: https://docs.hashicorp.com/sentinel/downloads [2]: https://docs.hashicorp.com/sentinel/intro/getting-started/ru... [3]: https://github.com/hashicorp/terraform-foundational-policies... [4]: https://github.com/hashicorp/terraform-guides/tree/master/go... [5]: https://github.com/hashicorp/terraform-guides/tree/master/go... [6]: https://github.com/hashicorp/terraform-guides/tree/master/go... [7]: https://github.com/hashicorp/sentinel-sdk [8]: https://docs.hashicorp.com/sentinel/commands/apply