Legally, and this is a bit crazy, but for example, if you buy a beautiful marker for the final resting place of a loved one, and it costs what, thousands of dollars? If I take a picture of that marker, *I* own the image. That is weird to me, and not something I could ever do. My Great Grandparents' shared headstone was snapped, & is at Find A Grave with a big ol' DO NOT TAKE THIS PHOTO written across it. It just makes me laugh now, it's not like Dale Chihuly crafted an image of it in exquisite blown glass, you took that with your phone. ;0)
Family Search could probably be sued into oblivion for breaking copyright law. They have rules, but zero oversight, so they're broken often. I feel like the Hall Monitor sometimes when I'm just shocked at what is posted there and try to encourage not posting an Obituary that was in the newspaper last month or copy/pasting an entire page from Find A Grave, or Wikipedia, or a history site.
I assume anything I post on the Internet will be taken, so I only share stuff that I don't mind other people having.
If you can find who posted something, ask. I know I would appreciate it, but I don't expect it. I've been pulling pix of state flowers recently to use at Find A Grave, and have tracked down every one that has a watermark. People have been very generous, and they're glad it might bring someone some solace. So do some checking, and for me, I don't post anything without permission or knowing it's in the public domain. And I assume the opposite with my "stuff'.