Fix license metadata: declare other with split LICENSE file

The card declared license: cc-by-4.0, which misstated the terms for
ERCOFTAC_AhmedBody25 and ERCOFTAC_WingBodyJunction. Both are curated
extracts of ERCOFTAC kbwiki material and inherit CC-BY-NC-SA-4.0.

- README frontmatter: license: other + license_name + license_link
- Add LICENSE recording the CC-BY-4.0 / CC-BY-NC-SA-4.0 split
- croissant.json root license now points at LICENSE
- Add configs block grouping the two license scopes
- Document that periodic-hill name digits are domain extents, not Re

Addresses Reviewer oEPR Q4.

LICENSE

@@ -0,0 +1,34 @@
+Closure Challenge v2 — licensing
+
+This dataset aggregates material under two different licenses. Which terms
+apply depends on which case directory the file sits in.
+
+--------------------------------------------------------------------------
+A. CC-BY-4.0
+--------------------------------------------------------------------------
+Applies to: alpha_05_4071_2024, alpha_05_4071_4048, alpha_15_13929_2024,
+alpha_15_13929_4048, AR_1_Ret_360, AR_3_Ret_360, AR_14_Ret_180,
+NASA_2DWMH, NASA_2DZP, NASA_2DN00, NASA_ASJ, NASA_FaithHill,
+and the evaluation_points directory.
+
+Upstream sources are public-domain or CC-BY: NASA Turbulence Modeling
+Resource, the Vinuesa duct database, and the Xiao parametric periodic-hill
+database. Full text: https://creativecommons.org/licenses/by/4.0/
+
+--------------------------------------------------------------------------
+B. CC-BY-NC-SA-4.0
+--------------------------------------------------------------------------
+Applies to: ERCOFTAC_AhmedBody25, ERCOFTAC_WingBodyJunction.
+
+These are curated extracts of ERCOFTAC kbwiki material (Classic Collection
+case082; DNS 1-6) and inherit the upstream CC-BY-NC-SA-4.0 terms, including
+the non-commercial and share-alike conditions.
+Full text: https://creativecommons.org/licenses/by-nc-sa/4.0/
+
+--------------------------------------------------------------------------
+C. Code
+--------------------------------------------------------------------------
+Extraction, plotting, and run scripts (*.py, *.sh) are MIT licensed.
+See LICENSE-CODE in the accompanying code repository.
+
+Per-case source attribution is in SOURCES.md in the code repository.

README.md

@@ -1,5 +1,7 @@
 ---
-license: cc-by-4.0
+license: other
+license_name: mixed-cc-by-4.0-and-cc-by-nc-sa-4.0
+license_link: LICENSE
 task_categories:
   - other
 language:
@@ -15,6 +17,21 @@ tags:
 pretty_name: "Closure Challenge v2 — extended ML-RANS turbulence benchmark"
 size_categories:
   - 100K<n<1M
+configs:
+  - config_name: cc_by_4_0_cases
+    data_files:
+      - path:
+          - data/alpha_*/**
+          - data/AR_*/**
+          - data/NASA_*/**
+          - data/evaluation_points/**
+        split: train
+  - config_name: cc_by_nc_sa_4_0_cases
+    data_files:
+      - path:
+          - data/ERCOFTAC_AhmedBody25/**
+          - data/ERCOFTAC_WingBodyJunction/**
+        split: train
 viewer: false
 ---
 
@@ -75,6 +92,10 @@ For each v2-new case:
 └── plots/                Pre-rendered comparison figures
 ```
 
+### Reading the periodic-hill case names
+
+The digits in `alpha_<slope>_<Lx>_<Ly>` are **domain dimensions, not Reynolds numbers**. `alpha_05_4071_2024` has streamwise extent x = 0 .. 4.071 and wall-normal extent y = 0 .. 2.024; `alpha_15_13929_4048` spans x = 0 .. 13.929 and y = 0 .. 4.048. The leading `alpha` value is the hill-slope parameter.
+
 ## Quick start
 
 ```python
@@ -88,9 +109,13 @@ For end-to-end scoring, use the `closure-challenge-v2` Python package and the `n
 
 ## License
 
-- **Code**: MIT (see `LICENSE-CODE` in the code repository)
-- **Curated data**: CC-BY-4.0 for all cases derived from public-domain or CC-BY upstream sources (NASA TMR, Vinuesa duct database, Xiao parametric PHLL, NASA wall-mounted hump, Faith Hill, NACA 0012)
-- **ERCOFTAC kbwiki extracts**: CC-BY-NC-SA-4.0 (Ahmed body case082, wing-body junction DNS 1-6) — inherited from upstream
+This dataset aggregates material under two different licenses. See the `LICENSE` file at the repository root for the authoritative statement.
+
+- **CC-BY-4.0**: the 12 non-ERCOFTAC cases (`alpha_*`, `AR_*`, `NASA_*`) and `evaluation_points`, derived from public-domain or CC-BY upstream sources (NASA Turbulence Modeling Resource, Vinuesa duct database, Xiao parametric periodic-hill database).
+- **CC-BY-NC-SA-4.0**: `ERCOFTAC_AhmedBody25` and `ERCOFTAC_WingBodyJunction`, curated extracts of ERCOFTAC kbwiki material (Classic Collection case082; DNS 1-6), inheriting the upstream non-commercial and share-alike conditions.
+- **Code**: MIT (see `LICENSE-CODE` in the code repository).
+
+Hugging Face has no per-directory license field, so this repository declares `license: other` and records the split in `LICENSE`. The `configs` block above groups the two license scopes for readers and machine consumers; it does not itself carry licensing force.
 
 Per-case attribution is in `SOURCES.md` of the code repository.
 

croissant.json

@@ -48,7 +48,7 @@
   "name": "closure-challenge-v2",
   "description": "Closure Challenge v2 — extended ML-RANS turbulence-modelling benchmark with composite scoring across 14 test cases (8 inherited from v1 plus 6 new engineering-relevant cases). The new cases bridge canonical 2D wall-bounded flows (NASA TMR: zero-pressure-gradient flat plate, NACA 0012 polar, axisymmetric subsonic jet) and 3D bluff-body separation (Ahmed body 25-degree slant, NASA Faith Hill, ERCOFTAC wing-body junction). For each case the dataset provides a baseline k-omega SST RANS prediction and a high-fidelity reference (DNS/LES, experimental PIV/LDA/PSP/FISF, or theoretical correlations).",
   "conformsTo": "http://mlcommons.org/croissant/1.0",
-  "license": "https://creativecommons.org/licenses/by/4.0/",
+  "license": "https://huggingface.co/datasets/anon-closure-challenge-v2/closure-challenge-v2/blob/main/LICENSE",
   "url": "https://huggingface.co/datasets/anon-closure-challenge-v2/closure-challenge-v2",
   "version": "0.4.0",
   "citeAs": "@inproceedings{closure_challenge_v2_neurips26, title={The Closure Challenge: A Benchmark Task for Machine Learning in Turbulence Modeling}, author={Anonymous}, booktitle={NeurIPS Datasets and Benchmarks Track (under review)}, year={2026}}",