I was reading about the Pedra Branca dispute before and found it quite fascinating. To get a better idea of the location of the islands involved, I ventured to OpenStreetMap to check them out, but to my surprise, while Pedra Branca and South Ledge are mapped, the Middle Rocks are not!
I then set course to add this feature to OSM, and iD-provided aerial imagery proved workable to trace the outline of the two islets, but not to assess the rest of objects on them. Would it be acceptable for me to use this YouTube video? What about this image I found on Google Images?
Simply, you need to check the license of the video and the picture. It does not matter how you find the picture
Youtube most probably not and the picture seems to be from the Royal Press Offices. While it might be they use an open license, if you are not able to find anything, its not viable.
If its unsure, don’t use it.
Its to avoid legal problems for openstreetmap. Though, you could still try to message the Royal Press Office and ask them if they allow you the usage of said picture for OpenStreetMap. Make sure to document this in the Wiki as well if you get the permission
If you are not clear, don’t use it and if its something else than public domain or CC0 or Open Data you should probably simply ask permission to use. There are some waiver templates in the wiki as well somewhere.
A YouTube video is the copyright of its creator. That prevents you, in theory at least, from redistributing the video, or a non-trivial excerpt from it, without the authorisation of the creator.
However, factual information in that video is probably not “the video or a non-trivial excerpt from it”. So, for example, if someone has gone for a leisurely walk around a town centre, filmed it, uploaded it to YouTube, and you spot a sign for a streetname that’s unmapped in OSM, it’s not a copyright infringement to use that information to update OSM.
(But if the same person has methodically gone round and walked every street in the city, zooming in on every street name, and uploaded the result? There’s a potential argument there that they’ve created a de facto database or compilation, and thus that might merit copyright protection in its own right or local database rights. Like I said, it’s complicated.)
(And… then there’s terms of use to consider. Google Maps has a clause that says roughly “by using this site, you agree that you won’t use features like Street View to update your own map database”, no matter what copyright law might say. I haven’t looked to see whether YouTube has anything like this because I try to avoid YouTube as much as humanly possible, though I doubt it.)
All this aside, @Negreheb 's broad point is correct - OSM is not a laboratory for interesting and creative interpretations of copyright law. We aim to create a map that everyone can use: sourcing data through debatable interpretations of copyright works against that. You should be fine taking isolated observations from YouTube videos, but please don’t do anything systematic.
