In order to create web content, a web content portlet is used. What technology is behind this portlet? What was used to develop this portlet? JSP, JSF, Struts, Icefaces, or any thing else?
Moreover, is there a link to download it separately.
It's using JSP, Java (using Liferay MVCPortlet) possibly some Alloy UI, and Struts 1 (as it's used throughout Liferay).
You can't download it separately, but the source code is there in the Liferay source archives. You just have to dig out Web Content Specific parts.