My understanding is that the clean room approach is tried and true and sufficient to avoid copyright infringement. So BigCo and other organizations that worry greatly about liability insist on it.
However I'm unaware of case law indicating that it's strictly necessary. If the final implementation differs enough from the original, no copyright infringement occurs and no one is going to sue anyone, so the steps taken to arrive at the new version are less relevant.
However I'm unaware of case law indicating that it's strictly necessary. If the final implementation differs enough from the original, no copyright infringement occurs and no one is going to sue anyone, so the steps taken to arrive at the new version are less relevant.