I've downloaded 3 from public trees, of my grandma, aunt and uncle. 2 are more than 100 years old so copyright, if any, should be expired.
Copyright is an awkward area.
In the UK, the rights on a photo expire 70 years after the death of the originator, not the date the photo was taken.
If you take a scan of a family photo which is out of copyright, the rights on that computer file expire 70 years after YOUR death. There are agencies such as Francis Frith and Getty Images which produce prints from very old negatives. The period on one of these starts when they issue the print.
Because of this, and the fact that the rules are different in other countries, the likes of Ancestry put clauses in their terms and conditions which in effect mean that if you upload anything, you give your rights over to them, and they can reuse those images for whatever purpose they like. If you don't actually have legal rights to an image, it becomes your fault if you upload to their website.
Images are so easily copied in this internet age that many organisations place "watermarks" on their images. Sometimes the marks are obvious, sometimes they are hidden as "noise" inside the image data. In the latter case it can be organised such that the offender can be traced.