Correct. jsp:include can only be used on an internal resource.
The JSTL <c:import> tag will do this for you. However, the code will still be running on website 2, and all website 1 gets is the result of running that code.
Another way is to use the java.net classes directly, and open your own HTTPConnection to WebSite2. The <c:import> tag does this under the hood anyway.
Hope this helps,
evnafets