It doesn't matter if it's hard to find the original PoP on the web. If the point was to make a piece of abandonware accessible to the public (and I question the assumption that PoP is abandonware), then you'd do that, not make a lazy clone of the game and put ads on it.

I think hosting abandonware is fine but it's totally not acceptable to try and make money from it. It's not your product to monetize, even if it's 20 years old.