“Although implementation guidance was released in November, many details are still unclear. It’s difficult to discern which journals and platforms will be considered compliant. (Conversely, some details of the plan seem mired in minutiae…)….

What does seem clear, at least in their implementation guidelines, is that Plan S will not permit publication in hybrid journals (a dominant model for society publishers) unless they meet one of two conditions: (i) The accepted manuscript is made available in a compliant repository at the time of publication without embargo with a Creative Commons Attribution license (CC BY) or equivalent (which permits both commercial and derivative reuse) (5). (ii) The article is published OA with a CC BY license in a subscription journal that has “transformative agreements,” which achieve compliance through agreements such as “Read and Publish” (6) during the no-more-than-3-year period before the journal must “flip” to full OA. With such restrictions, publishing in most hybrid society journals will likely be prohibited for authors with Plan S funders, even if their coauthors have other funding. As for PNAS, the journal allows authors to deposit in PubMed Central on publication with no embargo but only if the authors have paid the regular article charge and the OA CC BY surcharge, a funding arrangement that would not be allowed under Plan S. The uncertainty of how this change will affect authors and the journal are indeed part of the problem….

I also worry that a less diverse ecosystem of publishing models will be detrimental for researchers. Some journals are more selective than others and thus have higher publication fees because they process and review many papers compared with the number for which they collect fees. Authors willing to pay a higher fee if their papers are accepted by a more selective journal have that choice….”