Spoiler alert! This is more of a rant.
Recently, I was involved in the publication of an open-access paper that allowed to attach accompanying research artefacts such as data sets. The artefacts were all open-access (produced for that paper) but one artefact was not. It had been produced by the organizers of a workshop to specify a so-called “challenge”. The artefact was openly accessible but when the workshop gut published by a computer science society, it became copyrighted by this society and was moved behind its paywall.So, new open-access publications cannot just include this artefact in their accompanying data sets.
I regard this as a poisonous effect of paywalled artefacts. It creates insecurity with the authors about what they can publish. It slows down research. Do not accept such behavior of paywall publishers! Demand that your results are freely accessible under a generous license. We are researchers. We share!