The only responsability is for attribution? Then I think you have an ethical and contractual obligation to include it. Ship of Theseus or not, the ship you're c

The only responsability is for attribution? Then I think you have an ethical and contractual obligation to include it. Ship of Theseus or not, the ship you're currently riding on only exists because of their work. Even if you believe like me, that the current author is entitled to both primary authorship and ownership. Had you never started from their work, no ship, or an entirely different ship would exist instead. Even if there's so little left of the original that it's meaningless, you should still credit them if for historical context alone. Credit isn't a zero sum game. You don't lose value by including others contributions. You should be proud to accept credit for your work! You should be willing to share that credit as widely as you're able. And no one should ever feel guilty for standing on the shoulders of giants.