With, say, a commercial game (Kerbal Space Program in this instance) with user mods, that are themselves GPL3 licenced and have an effect on the visuals of a screenshot (e.g. art assets, images, custom displays), does a screenshot that includes these custom visuals have to automatically be licenced under the GPL?
My specific query is regarding the RasterPropMonitor plugin, which manages and renders real-time HUD screens. In this case, the whole project lists itself as GPL3, so I assume that automatically covers any attached images/textures, which would then undergo transformation/arrangement by the code - and then be visible on a screenshot.
I can reason how the project can be allowed to be GPL3, as it is "Downstream" from the (closed source) base game that it links with (I assume that Unity classes as a 'System Library'), but am troubled by whether everything that touches or relates to the base mod also ends up being GPL3 - e.g. someone who provides a custom screen, is using the GPL3 mod, so that work would also have to be GPL3?