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ADR-0006: License HaltSQL under MIT

  • Status: Accepted
  • Date: 2026-11-08
  • Deciders: Arnav Dadarya
  • Supersedes: ADR-0005
  • Related: LICENSE; NOTICE

Context​

ADR-0005 chose Apache-2.0. The maintainer prefers the MIT License: it is short, widely understood, and the same license as sql-guardrail, whose design inspired HaltSQL.

Decision​

  • License HaltSQL under the MIT License, copyright Arnav Dadarya.
  • Every package carries the same license identifier (MIT): the opam packages, the Python, MCP, TypeScript, Go and Java clients, the container image label and the OpenAPI document.
  • Keep NOTICE for third-party attributions (libpg_query, PostgreSQL, sql-guardrail).

Consequences​

  • MIT has no explicit patent grant, unlike Apache-2.0. Adopters who need one should know this.
  • Vendored libpg_query (BSD-3-Clause) and PostgreSQL (PostgreSQL License) sources keep their own licenses. Both are compatible with MIT distribution, and their license texts still ship in every release.
  • Test cases adapted from sql-guardrail are MIT, the same as the rest of the project, and are still attributed in the files that contain them.