| name | ke-dev-licensing |
| description | Licensing guardrail for ke developers: consult BEFORE adding ANY dependency. Covers the license-tiering policy (lean permissive core vs opt-in extras), the register of 6 license landmines (GPL Levenshtein/python-Levenshtein, LGPL TorchCP, non-commercial surya-ocr, GPL Potato, proprietary Prodigy) with their permissive replacements, scanner-invisible traps where license terms live in repo files not PyPI metadata (zss BSD-3, mistralai namespace pkg, PubTabNet CDLA), the rule that nothing copyleft or non-commercial is ever a default, and the CI license gate (pip-licenses/reuse) that fails the build on GPL/AGPL/non-commercial in core..hitl. Use when picking a metric/calibration/validation/OCR/agreement/HITL backend, adding to pyproject extras, choosing an edit-distance or conformal or annotation library, hitting a "GPL"/"non-commercial"/"RAIL"/"copyleft" license, deciding which extra a dep belongs in, or whether a dep needs import-only quarantine. |
| metadata | {"audience":"developers"} |
Read this BEFORE adding ANY dependency to ke. ke ships with a lean permissive core and a downstream-permissive promise: a consumer must be able to pip install ke and redistribute commercially with zero copyleft or non-commercial exposure. Everything that breaks that promise is opt-in behind an extra, quarantined, or excluded entirely.
Authoritative source: misc/docs/ke_06 -- library-landscape-and-integration-map.md (every license/version claim verified against live PyPI + GitHub mid-2026). Cite it, and re-verify primary sources before trusting any claim here.
The one rule
Nothing copyleft (GPL/AGPL/LGPL) or non-commercial is EVER a default. It is opt-in behind an extra, isolated, or out. The common case (pip install ke, no extras) resolves to MIT/BSD/Apache-2.0 only. Adding a backend is open-closed: it goes in an extra, you never edit a caller to take a new hard dep.
Decision procedure: "I want to add lib X"
- Find the real license. PyPI metadata lies (see traps below). Read the repo
LICENSE file AND scan the code headers. For model-driven libs, check the WEIGHTS/API license separately from the code license.
- Classify the license:
- Permissive (MIT/BSD-2/BSD-3/ISC/Apache-2.0): eligible for an extra, possibly core.
- Weak copyleft (LGPL): eligible ONLY as an import-only quarantined plugin with a permissive fallback. Never vendor, never patch, never static-bundle.
- Strong copyleft (GPL/AGPL): NOT a Python dependency. HTTP/out-of-process only, or design-reference only.
- Non-commercial / RAIL / proprietary: NOT shippable. Excluded; usable only behind an explicit, loudly-labelled non-permissive flag for internal research.
- Pick the tier/extra (table below). Core only if it's genuinely needed everywhere AND light AND permissive.
- Does it need quarantine? Only LGPL (e.g. TorchCP) goes import-only with a permissive fallback path.
- Add it as an extra in
pyproject.toml, behind @requires_extra for runtime-actionable install hints, and confirm the CI license gate still passes.
If X is one of the six landmines, stop and use the replacement.
The tier map (extras = dependency weight AND license)
pip install ke pulls only core. Everything else is an explicit extra.
| Extra | What goes in it | License posture |
|---|
core (always) | rapidfuzz (MIT), jiwer (Apache-2.0), pydantic (MIT), numpy, networkx (BSD-3), dol, config2py | permissive only |
metrics | sacrebleu (Apache-2.0), apted (MIT), zss (BSD-3), nervaluate (MIT), table-recognition-metric (Apache-2.0) | permissive |
calibration | netcal (Apache-2.0), scikit-learn (BSD-3), MAPIE (BSD-3), crepes (BSD-3), puncc (MIT) | permissive |
calibration-torch (heavy) | torch-uncertainty (Apache-2.0) — pulls torch | permissive |
calibration-graph (LICENSE-GATED, quarantine) | TorchCP (LGPL-3.0) — import-only | weak copyleft, isolated |
validation | jsonschema (MIT), fastjsonschema (BSD-3), pandera (MIT), pydantic-extra-types (MIT) | permissive |
constrained (heavy) | outlines (Apache-2.0), xgrammar (Apache-2.0) | permissive code (weights/API licensed separately) |
ocr / ocr-local (heavy) | tesserocr/pytesseract, rapidocr, python-doctr, easyocr, paddleocr, macOS ocrmac (all Apache-2.0/MIT incl. standard weights) | permissive |
ocr-cloud | google-cloud-vision (Apache-2.0), boto3+amazon-textract-response-parser/-textractor (Apache-2.0), azure-ai-documentintelligence (MIT), mistralai (Apache-2.0), mpxpy (MIT), openai (Apache-2.0), anthropic (MIT) | permissive clients; services are pay-per-call (a cost concern, not a license one) |
agreement | uqlm (Apache-2.0), lm-polygraph (MIT, heavy); ROVER builds on core rapidfuzz/jiwer | permissive (vet downloaded NLI/embedding weights; do NOT enable lm-polygraph's non-commercial COMET extra) |
hitl | label-studio-sdk (Apache-2.0), argilla (Apache-2.0), cvat-sdk (MIT) | permissive clients; servers run out-of-process |
| Excluded (license) | surya-ocr, Levenshtein/python-Levenshtein, Potato, Prodigy | NOT permissive — not installable extras |
The dependency direction ke -> ocracy is the ke[ocr] extra; never ocracy -> ke. ke core depends only on the OcrResult SHAPE, so it stays out of every OCR engine's license footprint.
The six landmines — keep these out of the permissive build
All verified against repo LICENSE files / PyPI license expressions in mid-2026.
| Library | Tier | License | Problem | Do instead |
|---|
Levenshtein | surface | GPL-2.0-or-later | program copyleft; disqualifying for permissive redistribution | rapidfuzz.distance.Levenshtein (MIT) — identical distance/ratio/editops/median, faster |
python-Levenshtein | surface | GPL-2.0-or-later | same; ALSO a transitive contaminant via legacy fuzzywuzzy code | rapidfuzz + CI gate to block the transitive pull |
TorchCP | calibration-graph | LGPL-3.0 (repo only; PyPI metadata blank) | weak copyleft — fine imported/dynamically linked, but patching or static-bundling triggers copyleft. The ONLY lib with graph-node & LLM-sequence conformal | quarantine in calibration-graph, import-only, never vendor/modify. Permissive fallback: torch-uncertainty/MAPIE/crepes for non-graph paths |
surya-ocr | ocr | code Apache-2.0; weights modified AI-Pubs Open RAIL-M (non-commercial above $5M funding/revenue) | highest-accuracy OCR but weights are non-commercial. The PyPI "Apache-2.0" classifier covers ONLY the code — a trap | keep out of ocr-local; expose only behind an explicit, labelled non-permissive engine flag for internal research under the threshold |
Potato | hitl | GPL-3.0-or-later (relicensed in v2.6.0) | strong copyleft would impose GPL on our distribution if linked | run as a separately-deployed standalone app over HTTP only (no code linkage), or prefer Label Studio |
Prodigy | hitl | commercial / proprietary (pay-once, closed source) | no open-source tier; cannot ship as a dependency | study its prefer_uncertain active-learning sorter as a design reference; build the equivalent on Label Studio / our own queue |
Scanner-invisible traps (the dangerous part)
License scanners read PyPI metadata. Some real terms live ONLY in repo files or weights — invisible to pip-licenses. These four are why a human + the CI gate must both check:
TorchCP — LGPL-3.0/GPL-3.0 detected by GitHub, but PyPI metadata carries no license field → scanners flag "unknown," not "copyleft."surya-ocr — PyPI Apache-2.0 classifier reflects the CODE only; the non-commercial RAIL-M terms live with the weights.zss — actually BSD-3-Clause, NOT MIT (PyPI omits the classifier; read the vendored LICENSE). Still permissive — a correction, not a blocker.- PubTabNet — repo top-level
LICENSE.md is CDLA-Permissive-1.0, but only src/metric.py carries the Apache-2.0 header we actually rely on. Cite the FILE header, not the repo license.
mistralai — PyPI license=None (file-only Apache-2.0); also a namespace package → import from mistralai.client import Mistral, not from mistralai import Mistral. License-clean once you read the repo LICENSE.nonconformist — genuinely MIT per its repo despite a blank PyPI license field; avoid on staleness grounds (~9 yrs), not license.
Rule of thumb: PyPI "unknown"/license=None ≠ permissive. Open the repo LICENSE, and for any model-driven lib, the weights/API license too.
The CI license gate (must exist, must fail the build)
A CI gate (pip-licenses and/or reuse) MUST fail the build if anything resolving in core through hitl (i.e. the shippable extras) is GPL/AGPL/non-commercial. It is the safety net for two failure modes:
- Transitive contamination —
python-Levenshtein sneaks in via legacy fuzzywuzzy-style code.
- Metadata-blind copyleft —
TorchCP/surya-ocr carry their terms only in repo files, so a pure-metadata scan misses them; the gate must treat "unknown" license as a failure (or maintain an explicit allowlist) and must scope-exclude only the explicitly-quarantined calibration-graph extra and the labelled non-permissive research flags.
The gate is necessary because scanners alone will miss the repo-file traps above — never rely on a green scanner as proof of compliance.
Runtime hints
Optional backends raise actionable install hints via the @requires_extra decorator (registry-resolved strategy protocols, injected keyword-only with smart defaults; open-closed via entry points). A missing extra tells the user exactly which pip install ke[...] to run. The non-permissive research flags (surya, etc.) must additionally warn loudly at the call site that the chosen engine is non-shippable.
When in doubt
If you cannot determine a library's true license from primary sources, treat it as non-permissive and do not add it to a shippable extra. Flag it for the maintainer. A wrong permissive assumption poisons every downstream consumer of ke.
