> So, I as a mere human can't possibly determine what's public domain and what isn't?
You can, just look at the license. If one is missing, assume it's copyrighted.
> I have to put in the effort to track down the original source, and see what notes he/she/it/them put on the original, and if the creator wrote "released into public domain" you can go ahead and use it?
Yes? I don't see what's wrong with that, asking the author if you can use his work is just good etiquette, I'm sorry if that's too much work for you.
> I don't see what's wrong with that, asking the author if you can use his work is just good etiquette, I'm sorry if that's too much work for you.
Yes, it is too much work; it's often not even possible. This is the problem of orphaned works, where the authors are gone or missing and nobody knows who they are, etc, or the work was published anonymously, etc.
Tracing down the authors of works produced seventy or eighty years ago is actually really difficult. You should try it sometime before casually dismissing the concern as being born of laziness.
You can, just look at the license. If one is missing, assume it's copyrighted.
> I have to put in the effort to track down the original source, and see what notes he/she/it/them put on the original, and if the creator wrote "released into public domain" you can go ahead and use it?
Yes? I don't see what's wrong with that, asking the author if you can use his work is just good etiquette, I'm sorry if that's too much work for you.