What they can do is resell things in the public domain, what they can't do is shake people down for licensing fees
This is not sleazy? It's in the first paragraph, nearly the first sentence. They sent a demand letter to the one that actually took theses photographs.
There are sites that have public domain images and google has easy to use tools that sort images by licensing types. I make art and when I do need a reference picture, I use these tools. Most folks can do these things easily.
What Getty images does is sleazy because it makes it so that some of the tools available won't show a picture. Getty is charging for it and licensing it. This is different than them doing the work - they are taking it away.
I can use CentOS workout pay dime to Red Hat.
* typo
If it is indeed work to find and catalogue those images then they are allowed to charge for access to that catalogue. But a public domain image cannot be licensed.