microimpute has no licence, so all rights are reserved #197

microimpute has no licence. There is no LICENSE file, no license field in pyproject.toml, no licence classifier, and no licence section in the README:

$ git ls-files | grep -i licen     # (no output)
$ gh api repos/PolicyEngine/microimpute --jq .license
null

PyPI carries the same gap — all 53 releases, including 3.1.1, publish license: None with no classifiers.

Why this matters beyond JOSS

Without a licence, default copyright applies and the work is all rights reserved. Nobody has permission to use, copy, modify or redistribute it, including the repositories that already depend on it: policyengine-uk-data, uk-trade-shock-study, uk-public-services-imputation, nics-exemption-inactive-employees, and imputation-paper. policyengine-uk-data is a production pipeline, so this is not hypothetical.

It is also a hard blocker for the JOSS submission planned in the paper PR — "does the repository contain a plain-text LICENSE that is OSI approved?" is the first item on the review checklist.

Suggested fix

Add MIT at the repository root, matching microdf and the rest of the organisation, and record it in packaging metadata:

[project]
license = "MIT"
license-files = ["LICENSE"]
classifiers = ["License :: OSI Approved :: MIT License"]

Then cut a release so the PyPI metadata carries it.

Because this is a relicensing of existing work rather than a new file, it needs agreement from the substantial copyright holders — @juaristi22 (~354 commits), @MaxGhenis (~101), @nikhilwoodruff (~45) — and ideally from @baogorek, who contributed 15.