Prior to Alfresco 4.x Portlet support was built directly into Share. This meant that the Share source code contained lots of logic (in particular, lots of if blocks) that altered the behaviour of the application if it was detected that the code was being run in a portlet context. As a proof of concept for the extensibility features that we added to Surf we abstracted all the Portlet support code from Share and placed it in an extension module. This module is included in the Share code but is not deployed by default.
Essentially if you wish to use the Alfresco portlets (e.g. through LifeRay) then you need to ensure that you have deployed the Portlet module - the best way to do this is to switch Share to run in "auto-deploy" mode so that the module is automatically deployed at application startup.
Regards,
Dave