here is my working environment.
First download the latest jems-installer 1.2.0CR1.
Install the AS with the ejb3 profile, then deploy the portal.
If you need seam then you will have to download the latest
package.(1.1.0CR2) The examples without ajax will work out of the
box. If you want to use ajax you will have to download the latest
ajax4jsf library and replace the jars. After that the ajax examples
But I don't know if you can develop a working portlet using seam within
the portal 2.6 at the moment.