In general, publisher means this location is provided by the article's original publisher, through the canonical doi.org URL, as a Published or Accepted version. For example, the full text of https://doi.org/10.3390/polym10111254 is available from MDPI and the corresponding OA location looks like this:
{
"host_type": "publisher",
"pmh_id": null,
"updated": "2019-11-12T05:55:06.811259",
"version": "publishedVersion",
"url_for_landing_page": "https://doi.org/10.3390/polym10111254",
"license": "cc-by",
"url": "https://www.mdpi.com/2073-4360/10/11/1254/pdf",
"endpoint_id": null,
"repository_institution": null,
"evidence": "open (via page says license)",
"oa_date": "2018-11-12",
"is_best": true,
"url_for_pdf": "https://www.mdpi.com/2073-4360/10/11/1254/pdf"
}
The notable exception is preprint repositories, which we call repository even though the preprint may be the final version of the document represented by the DOI. For example, https://doi.org/10.21203/rs.2.23921/v1 is available from Research Square, but its OA location looks like this:
{
"url_for_pdf": "https://www.researchsquare.com/article/rs-14482/v1.pdf",
"oa_date": "2020-02-19",
"evidence": "oa repository (via page says license)",
"is_best": true,
"host_type": "repository",
"url_for_landing_page": "https://doi.org/10.21203/rs.2.23921/v1",
"pmh_id": null,
"license": "cc-by",
"url": "https://www.researchsquare.com/article/rs-14482/v1.pdf",
"version": "submittedVersion",
"repository_institution": null,
"updated": "2020-08-27T18:26:50.464062",
"endpoint_id": null
}
The more common case where host_type is repository is in institutional repositories, often managed by an institution one of the authors is affiliated with. https://doi.org/10.1039/c3cp54043j isn't available from the RSC, but it is in Refubium. This location looks like this:
{
"endpoint_id": "tfns8wvw5hkwxjnh5ysu",
"host_type": "repository",
"repository_institution": "Universit\u00e4tsbibliothek der Freien Universit\u00e4t Berlin - Refubium",
"url": "https://refubium.fu-berlin.de/bitstream/fub188/15972/1/c3cp54043j.pdf",
"is_best": true,
"url_for_landing_page": "https://refubium.fu-berlin.de/handle/fub188/15972",
"pmh_id": "oai:refubium.fu-berlin.de:fub188/15972",
"license": null,
"updated": "2020-11-02T03:49:56.084478",
"evidence": "oa repository (via OAI-PMH doi match)",
"version": "submittedVersion",
"oa_date": null,
"url_for_pdf": "https://refubium.fu-berlin.de/bitstream/fub188/15972/1/c3cp54043j.pdf"
}