24. Apache-2.0 for the code, amending ADR 0006

Context

ADR 0006 chose MIT for the code and CC BY 4.0 for the catalogue, and the second half of that decision has held up: the catalogue's value is its sourcing, and CC BY is the licence that makes credit a condition of reuse rather than a courtesy.

The first half was chosen for adoption alone. Two things it does not do turn out to matter. MIT requires that the copyright notice be retained and says nothing further, so a fork that keeps a line in a file has satisfied it while presenting the work as its own; and MIT is silent on both patents and trade marks, so the project's name — the one asset a fork cannot take without renaming — has no licence-level protection at all.

This is decided now because the cost of deciding it later is not symmetric. Before the first release the copyright holder is one person. After it, relicensing needs the consent of everyone who has contributed since.

Decision

The code is Apache-2.0. A NOTICE file carries the attribution, and section 4(d) of the licence requires every derivative distribution to carry it too. Section 6 grants no trade mark rights, so the name stays with the project. The patent grant and its termination clause come along, which MIT has no equivalent of.

The catalogue stays CC BY 4.0. Nothing in ADR 0006's data rule changes: language data is still audited before it lands, anything copyleft still stays behind an extra, and every data source still needs an ADR of its own.

Per-file Apache headers are deliberately not used. They are a convention of the licence, not a requirement of it, and 118 procedure modules whose docstrings carry the reasoning behind each checker would be worse documents with eleven lines of boilerplate on top. LICENSE and NOTICE carry the terms; the distributions carry both.

Because the licence expression must describe what a distribution actually contains and not only what its author wrote, the three published distributions declare compound SPDX expressions: Apache-2.0 AND CC-BY-4.0 for denckring, which ships the catalogue; Apache-2.0 AND CC-BY-4.0 AND BSD-2-Clause for denckring-en-data, which ships Open English WordNet and the CMU Pronouncing Dictionary; and Apache-2.0 AND CC0-1.0 for denckring-de-data, which ships Wikidata Lexemes.

Consequences

A fork must carry the NOTICE, must rename to publish, and gains no claim on the name. None of that prevents a fork, and no licence does — what it prevents is a fork that presents itself as the original.

The obligation ADR 0006 created is now paid rather than merely stated: the wheel that ships catalogue.yaml also ships LICENSE-DATA, so the CC BY terms reach the people who install the package and never see the repository.

Apache-2.0 is incompatible with GPLv2-only code, which MIT was not. No dependency here is GPLv2-only, and a Python library acquiring one is unlikely, but a future dependency audit has one more question to ask than it did.