To quote @Finnusertop on mediawiki.org
"According to Wikimedia Foundation's resolution on licensing policy (https://wikimediafoundation.org/wiki/Resolution:Licensing_policy), all content on Wikimedia projects should be free, with the exception of those non-free files used under a fair-use doctrine (or similar). According to the resolution, such uses are conditioned by the projects' Exemption Doctrine Policies (EDP). The resolution goes on to say that exceptions granted by the EDPs should be minimal. The English Wikipeda's EDP is "Wikipedia:Non-free content" (https://en.wikipedia.org/wiki/Wikipedia:Non-free_content). It stipulates that a non-free file may only be used in those articles that a specific, relevant and valid non-free use rationale is written for."
Various project policies do not allow non-free image use https://en.wikipedia.org/wiki/Wikipedia:Non-free_content#Non-free_image_use_in_galleries
AS a result projects such as mobile apps, RelatedArticles, Gather, and mobile web search violate local policy.
PageImages the extension responsible for this choice of image should have a configuration option to avoid picking images where the license on that wiki doesn't permit it.