The owner obviously won't take you to court, he didn't even care enough about his website to keep it online. He de facto took his work and threw it in the trash, and you found it.
You can also use Wayback Machine to retrieve some more pieces of the website.
I think the right way to go is to use whatever you can, recycle it but not by copy/pasting but by rewriting the article while using the old article as a template, and then somewhere on the site put a thank you note to the original author.
That way the new article would be yours, based on a resource, and the resource would get the due credit. All good. But copy/paste? No.
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