Copyright tends to lean more towards someone making a profit out of someone elses work.
Things like books, and to an extent art work means you can't particularly copy the work without permission.
But people do it all the time. You will have already broken copyright law in your life before and will do it again.
Stick a source next to the photo and you'll more than likely be fine.
Hmmmm......
Copyright means just that. You cant copy it !! There's no
particularly about it.
However, I will say this.
You are always better off asking the copyright holders permission and stating that you will clearly state who the owner of the material is, along with any relevant website links.
Why ?
Because, as an ex professional motorsport photographer who did have photo's copied from my website (which were watermarked) without permission and published on other websites without my permission.
I can categorically say that if the persons had asked and said they would link to the source of the photo it would of been fine. But as they couldn't be bothered and gave a b*lls**t excuse when challenged, i really had little choice other than to request that they were removed.
You are right in stating that its more to do with financial matters.
As basically it amouts to walking into a newsagents and nicking a 2p lollipop. In the grand scheme of things its only 2p (which the newsagent maybe able to afford writing off). BUT its still theft.
However, as i said above, if the copyright holder is going to get free advertising from it (so potentially a benefit i.e.both parties win), your more likely to get a far more positive response