JBoss Portal is the whole thing, an open source portal implementation.
It consists of several parts, one of them is the module "Portlet Container". The "Portlet Container" is the runtime-environment of the JSR-168/JSR-286-Portlets.
The Portlet-Bridge is kind of optional. If you want to use web-frameworks within a portlet, you need bridges between the worlds. The JBoss Portlet Bridge brings JSF-support to Portlets (...and Seam and RichFaces).
To start, go and get "JBoss Portal + JBoss AS 4.2.3" here:
The Portlet-Container is part of this package, you don't need to download or integrate this manually. If you want to use JSF, Seam and RichFaces go and get the Portlet Bridge also. http://labs.jboss.com/portletbridge/download/