OpenTofu

OpenTofu is a fork of Terraform created in September 2023 when HashiCorp changed Terraform's license from MPL 2.0 (open source) to BSL 1.1 (source-available, with commercial restrictions). The Linux Foundation adopted the project to ensure a truly open source alternative existed.

Why it exists

The timeline

1. 2014-2023 — Terraform under MPL 2.0 license (permissive open source)
2. August 2023 — HashiCorp switches to BSL 1.1 (prohibits competitive products)
3. September 2023 — OpenTF manifesto signed by 100+ companies
4. October 2023 — Linux Foundation adopts the project as OpenTofu
5. January 2024 — OpenTofu 1.6.0 (first stable release)

What does BSL 1.1 prohibit?

Terraform's BSL 1.1 license allows using, copying, and modifying the code, but prohibits offering a competitive product based on it. This affects:

• Companies offering Terraform-as-a-Service
• IaC platforms integrating Terraform
• Managed services competing with Terraform Cloud

For end users who only use Terraform internally, the practical impact is minimal.

Compatibility

OpenTofu maintains compatibility with the Terraform ecosystem:

# Basic migration
# 1. Install OpenTofu
brew install opentofu
 
# 2. Replace commands (drop-in replacement)
tofu init       # instead of terraform init
tofu plan       # instead of terraform plan
tofu apply      # instead of terraform apply
 
# 3. State file is compatible
# No state migration required

What is compatible?

• .tf files in HCL — 100% compatible
• Terraform Registry providers — work directly
• Existing modules — no changes
• State files — compatible format
• Backend configurations — S3, GCS, Azure, etc.

What diverges?

OpenTofu has started adding its own features:

• State encryption — native state file encryption (not available in Terraform OSS)
• Early variable/locals evaluation — early evaluation of variables
• Own registry — registry.opentofu.org as an alternative

When to choose OpenTofu

Choose OpenTofu when:

• Open source licensing is a requirement (compliance, corporate policy)
• You build products or services on top of the IaC tool
• You want to contribute to the project's development
• You need native state encryption
• You prefer Linux Foundation governance

Stay with Terraform when:

• You use Terraform Cloud/Enterprise and its exclusive features
• The team is already trained on Terraform and there's no licensing reason to switch
• You need commercial support from HashiCorp
• Stability of the established ecosystem is priority

Direct comparison

Practical example

# main.tf — works the same in Terraform and OpenTofu
terraform {
  required_version = ">= 1.6.0"
 
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 5.0"
    }
  }
 
  backend "s3" {
    bucket = "my-state-bucket"
    key    = "prod/terraform.tfstate"
    region = "us-east-1"
  }
}
 
provider "aws" {
  region = "us-east-1"
}
 
module "vpc" {
  source  = "terraform-aws-modules/vpc/aws"
  version = "5.5.0"
 
  name = "production"
  cidr = "10.0.0.0/16"
}

State encryption (OpenTofu exclusive)

# OpenTofu only
terraform {
  encryption {
    key_provider "pbkdf2" "main" {
      passphrase = var.state_passphrase
    }
 
    method "aes_gcm" "main" {
      keys = key_provider.pbkdf2.main
    }
 
    state {
      method = method.aes_gcm.main
    }
  }
}

Ecosystem and adoption

Companies backing OpenTofu:

• Spacelift — IaC platform, main contributor
• env0 — IaC platform
• Scalr — Terraform/OpenTofu management
• Gruntwork — IaC tools (Terragrunt)
• Harness — CI/CD platform

Why it matters

Terraform's license change to BSL was a turning point for the IaC ecosystem. OpenTofu ensures that investment in HCL knowledge and existing modules is not locked behind a restrictive license. For organizations that value open source as a principle, not just a convenience, OpenTofu is the viable alternative.

References

• OpenTofu Documentation — Linux Foundation, 2024. Official documentation.
• OpenTofu Manifesto — OpenTofu, 2023. The original manifesto with signatories.
• HashiCorp BSL FAQ — HashiCorp, 2023. Official explanation of the license change.
• OpenTofu vs Terraform — OpenTofu, 2024. Official migration guide.
• The Future of Terraform Must Be Open — Yevgeniy Brikman, 2023. Perspective from the author of "Terraform: Up & Running."
• OpenTofu vs Terraform — Spacelift, 2024. Detailed comparison between OpenTofu and Terraform.