Thanks for your question. All articles available via the Europe PMC bulk download are part of the Open Access subset and are free to read, use, text mine, reference, and cite (CC BY and CC0).
That said, copyright compliance remains the responsibility of the user. If you plan to reuse substantial parts of an article such as figures, images, or tables, you should review the specific license attached to each article.
For programmatic license checks, the Europe PMC Search API supports filtering by license using the LICENSE field, see the search syntax reference for details.
You can also retrieve availability and license fields from the API response.
More details can found here,
https://europepmc.org/RestfulWebService
https://europepmc.org/docs/EBI_Europe_PMC_Web_Service_Reference.pdf.
Hope this helps.
Thanks,
Madhu