Hi,
Yes you read it right.
If your page not contains any dynamic content then it is better to use <%@ include file="copyleft.html" %> include directive.
But if your include page contains dynamic data then better to use Standard action <jsp:include ..../>
basically <jsp:include ..../> use to include the page response at run time so it takes time to compile ....
When inclide directive just copy the file contains and Past it on given location ......... So it is fast.... compare to <jsp:include ..../> standard action.