You lost me at <i>&quot;…API (such as a website)&quot;…</i>.  How is a website an API?  UI I can see, but API?  What do you mean by that?<p>In the case of UI, there&#x27;s a good chance that, to the extent that the piece that is copied constitutes a <i>method of operation</i>, that piece is not copyrightable.  For example, in Lotus v. Borland [1], the court ruled that the organization of menus and keyboard macro commands for the sake of compatibility was not copyrightable.  However, certain more &quot;artistic&quot; things like icons and such are copyrightable.<p>[1]: <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Lotus_Development_Corp._v._Borland_International,_Inc" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Lotus_Development_Corp._v._Bor...</a>.