I'm using a dataset of imagery that is provided by Open Aerial Map. Their license terms are:

All imagery is publicly licensed and made available through the Humanitarian OpenStreetMap Team's Open Imagery Network (OIN) Node. All imagery contained in OIN is licensed CC-BY 4.0, with attribution as contributors of Open Imagery Network. All imagery is available to be traced in OpenStreetMap.

By submitting imagery to OpenAerialMap, you agree to place your imagery into the Open Imagery Network (OIN) through OpenAerialMap. The original copyright remains with the original source or holder of the imagery but you grant OAM to license the imagery as CC-BY 4.0, with attribution as contributors of Open Imagery Network. All imagery is available to be traced in OpenStreetMap.

Each image, as provided to Open Aerial Map, also comes with its additional licensing metadata which varies between CC-BY, CC-BY-NC and CC-BY-SA.

Here's an example of such a conflict: https://api.openaerialmap.org/meta/5ce4b726acfb8e0006396f98 (top level metadata says CC-BY 4.0, while the image is CC-BY-NC).

  "meta": {
    "provided_by": "OpenAerialMap",
    "license": "CC-BY 4.0",
    "website": "http://beta.openaerialmap.org",
    "page": 1,
    "limit": 100,
    "found": 12614
  "results": {
    "_id": "5ce4b726acfb8e0006396f98",
    "acquisition_end": "2019-05-15T16:00:00.000Z",
    "acquisition_start": "2019-05-15T15:00:00.000Z",
    "contact": "-",
    "platform": "uav",
    "provider": "-",
    "properties": {
      "license": "CC BY-NC 4.0",
      "sensor": "RGB",
      "crs": "EPSG:3100",
      "dimensions": [

  • Are these licenses effectively converted to CC-BY 4.0 by the terms of submission?


I contacted OAM with no response.

See also the upload form, where this is explained to users:

enter image description here

  • In principle it's possible for a work to be available under multiple distinct licenses, in which case it's up to the consumer to choose which license they use it under. However in the specific case, it depends whether the work really has been made available under both licenses. If the CC-BY license rules are not made sufficiently clear during the submission process, then the copyright-holder might be successful in arguing that they never intended to grant that license. If they used a submission form with a menu which allowed them to choose a different license, that would help their case.
    – kaya3
    May 15, 2023 at 20:44
  • So there's sort of two different things you could be asking here ─ (1) If a work has been made available under two different licenses, or it's ambiguous which of those two licenses applies, what should the consumer do about it? (2) Could a copyright-holder who submits photos to the Open Aerial Map project argue that their photo is not available under CC-BY despite this being stated in their license terms?
    – kaya3
    May 15, 2023 at 20:47
  • @kaya3 the first really. If a distributing organisation declares that their content is licensed by CC-BY, then as a consumer of that data, do I assume that CC-BY is appropriate? If I hadn't checked the metadata I wouldn't have noticed. The simplest approach is to exclude any data that is tagged with -NC or -SA, but it seems odd that the overarching terms exist whilst also asking users to specify what terms their data are licensed as.
    – Josh
    May 16, 2023 at 9:24
  • How to resolve (apparently) conflicting terms is a common problem of contract law, so that’s definitely a good legal question. However, the practical solution is clearly to email OAM saying "your terms say license X, the metadata say license Y, I am going to assume dual-license unless you tell me otherwise".
    – KFK
    May 16, 2023 at 9:55
  • 2
    Also, you cannot rely on the submission terms. Maybe uploaders were able to select various licenses in the past, then OAM added the language "by uploading you agree to CC-BY" afterwards. In that case an image uploaded before that change, but available after, would not be CC-BY.
    – KFK
    May 16, 2023 at 9:57

1 Answer 1



CC is set up in a way, that you can not put any item acquired under one license under a more permissive license set in any way without breaching the license terms.

A work that is CC-BY-NC can not become just CC-BY under the terms of the CC-BY-NC, as the -NC does not allow that part to be dropped as the CC-BY-NC license text demands you can't license the new work in any fashion that allows commercial use.

It's only allowed to transmit into a more restrictive license scheme (e.g. adding -NC, -ND, or -SA), and never possible to drop a -NC, -ND or -SA.

There is one exception: if something is already under a Share Alike license, you can not tack on any limitations either! A ...-SA license can not be changed to any other license type at all, not CC-BY-NC-SA, not more permissive, not less permissive, not even an equivalent license scheme. The license terms on such a work is permanently fixed if you get it under that license.

Which license applies?

It is unsure if the author or someone that received the work under a more permissive license than CC-BY-SA/CC-BY-NC did grant just OAM a license under CC-BY. In case there is a claim against OAM, it would be the duty of OAM to prove that they had received the work under this license and thus could grant it under CC-BY.

The diligent thing for someone receiving the work down the line from OAM would be to presume the work to be under the most restrictive license that can be found in the metadata. In case those are incompatible with the proposed use, then the item can't be used.

  • 1
    For reference OSM also provides this text, which seems relevant: wiki.osmfoundation.org/wiki/Licence/…
    – Josh
    May 16, 2023 at 9:34
  • @Josh wjich simply is not possible under the CC-license sheme.
    – Trish
    May 16, 2023 at 9:52
  • That answer is correct under the assumption that OAM was granted a CC-BY-NC license only (in which case, they are not allowed to unilaterally re-license as CC-BY). However, it might be that CC-BY was granted at the original upload.
    – KFK
    May 16, 2023 at 10:00
  • 1
    The question of how hard reusers are supposed to check that the offered license is proper is a good one, but there is definitely some leeway (safe harbor in the US etc. - probably highly jurisdiction-dependent).
    – KFK
    May 16, 2023 at 11:41
  • 2
    @Josh it’s badly written, but the way I read "all imagery is licensed CC-BY (...) and specific additional SA/NC if selected upon upload", OAM accepts uploads under CC-BY-NC. As Trish's answer explains, such uploads cannot unilaterally be relicensed as CC-BY.
    – KFK
    Jul 18, 2023 at 8:31

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