# Licences

This dataset is a **collection of 1,691 separately licensed photographs**, 
not a single relicensed work. Each row keeps the licence it arrived with, recorded in 
its own `license`, `license_spdx` and `license_url` columns. Nothing here relicenses 
any photograph, and the repository-level licence tag is metadata rather than a grant.

## Inventory

| Licence | SPDX | Files | Deed |
|---|---|---:|---|
| CC BY-SA 4.0 | CC-BY-SA-4.0 | 896 | <https://creativecommons.org/licenses/by-sa/4.0/> |
| CC BY-SA 3.0 | CC-BY-SA-3.0 | 668 | <https://creativecommons.org/licenses/by-sa/3.0/> |
| Public domain | — | 52 | <https://creativecommons.org/publicdomain/mark/1.0/> |
| CC BY 4.0 | CC-BY-4.0 | 21 | <https://creativecommons.org/licenses/by/4.0/> |
| CC BY 3.0 | CC-BY-3.0 | 19 | <https://creativecommons.org/licenses/by/3.0/> |
| CC BY 2.0 | CC-BY-2.0 | 15 | <https://creativecommons.org/licenses/by/2.0/> |
| CC BY-SA 3.0 pl | CC-BY-SA-3.0-PL | 9 | <https://creativecommons.org/licenses/by-sa/3.0/pl/> |
| CC0 | CC0-1.0 | 7 | <https://creativecommons.org/publicdomain/zero/1.0/> |
| CC BY-SA 2.0 | CC-BY-SA-2.0 | 3 | <https://creativecommons.org/licenses/by-sa/2.0/> |
| CC BY-SA 2.5 | CC-BY-SA-2.5 | 1 | <https://creativecommons.org/licenses/by-sa/2.5/> |

## Modification

**1,538 of the 1,691 files are modified**: they were downscaled to at most 2000 px on the long edge and re-encoded; EXIF not preserved. 
The remaining **153 are byte-identical to the Commons original**. 
The `modified` column says which, and it is derived by comparing the stored bytes 
against the Commons digest in `commons_sha1` rather than asserted — so you can check 
it rather than trust it.

## Public-domain files

Files recorded as *Public domain* carry the Creative Commons Public Domain Mark, 
which is a label rather than a licence: it asserts freedom from known copyright 
without saying on what basis. The `license_template` column carries the Commons 
template naming that basis where it could be retrieved.

## What you must do

- **Attribute each photograph to its own photographer.** The `attribution_text` 
  column is a ready-to-paste credit line; `credits.csv` carries all of them.
- **Keep the licence with the row.** If you redistribute a subset, filter 
  `credits.csv` to it and ship that too.
- **Say the files are modified** where `modified` is true. They are adaptations.
- **ShareAlike binds your adaptations**, not this collection. If you crop, augment 
  or composite a CC BY-SA photograph, release the result under that photograph's own 
  licence version. Because this collection spans CC BY-SA 2.0 to 4.0, an arbitrary 
  slice inherits a *mix* of obligations — filter by `license_spdx` first if you need 
  a single-licence derivative.
- **Add no further restrictions.** No terms are imposed here and none may be added.