Regardless of whether you are using JetSpeed2 or not, this tutorial demonstrates how to add the appropriate jar files to your classpath, and allow your portlet to run. The appropriate libraries are supplied with JetSpeed2 when you download and install it. With WebSphere, they come packaged along with the WebSphere Portal Development Toolkit.
Even though everything is in place, the JSP editor coughs up on the custom tags, and it's not allowing you to reference the renderRequest or renderResponse, or any of those 'implicit objects' that are supposedly available if use the portlet custom tags.
If you look at a few of my tutorials on creating JSPs with IRAD on my website (check out my signature links), you'll see the same error message. Still, when I deploy the apps, they all deploy fine.