Keyboard shortcuts

Press ← or → to navigate between chapters

Press S or / to search in the book

Press ? to show this help

Press Esc to hide this help

ADR-0004: Apache-2.0 license and DCO

Note

Architecture decision: accepted.

Context and problem statement

Shiin is open-source software intended for adoption by developers and teams. It needed a license that is permissive enough for commercial and personal use, includes a patent grant, and is well understood by the ecosystem. Contributions needed a lightweight sign-off mechanism, not a separate contributor license agreement that creates friction for first-time contributors.

Decision drivers

  • Permissive enough for broad adoption, including by agent vendors.
  • Patent protection for contributors and users.
  • Minimal contribution overhead.
  • Compatibility with the Cedar dependency’s license.

Considered options

  1. Apache License 2.0 with Developer Certificate of Origin.
  2. MIT License.
  3. BSD 3-clause.
  4. A contributor license agreement in addition to the license.

Decision outcome

Chosen option: “Apache License 2.0 with Developer Certificate of Origin”, because Apache 2.0 provides an explicit patent grant that MIT and BSD do not, and the DCO adds no contributor friction.

  • The license is Apache-2.0, as set in [workspace.package].license in Cargo.toml.
  • Every commit requires a DCO sign-off (git commit -s); no contributor license agreement is used.
  • This choice is recorded in ADR-0004 and referenced from CONTRIBUTING.md.

Consequences

  • Good, because contributors and users get a well-understood license with patent protection.
  • Good, because the DCO sign-off is a one-line commit flag, not a separate document to sign.
  • Bad, because Apache 2.0 is slightly longer than MIT or BSD, though this does not affect usage.

Confirmation

  • The LICENSE file and NOTICE file are present at the repository root.
  • All crates inherit license = "Apache-2.0" from the workspace.

Pros and cons of the options

Apache 2.0 with DCO

  • Good, because of the explicit patent grant.
  • Good, because DCO is lightweight.
  • Bad, because it is longer than MIT.

MIT

  • Good, because it is short and widely recognized.
  • Bad, because it has no explicit patent grant.

BSD 3-clause

  • Good, because it is short and permissive.
  • Bad, because it lacks a patent grant and adds a clause that rarely matters in practice.

Contributor license agreement

  • Good, because it gives the project legal flexibility.
  • Bad, because it creates friction for contributors and conflicts with the goal of minimal overhead.

More information

The DCO is documented at developercertificate.org. The Apache 2.0 license text is in LICENSE. Attribution notices are in NOTICE.