Earlier quoted context omitted.
Not everybody likes to hear it, but archive.is is an illegal operation. In some countries, posting archive.is links may even be illegal as well (it might be interpreted by a court as "Aiding and Abetting Criminal Copyright Infringement")
is it still illegal if it's the exact same page including ads (revenues go to the source) ?
It's generally not thought to be illegal, see for example: https://www.practicalecommerce.com/Search-Engines-Indexing-a...