As you probably have seen, the forums on ez.no have been closed, so there will be no headache about where to post.
Projects.ez.no should imho be heavily integrated here, not duplicated - the first step being the projects forums being imported to here and closed over there.
Principal Consultant International Business
Member of the Community Project Board
The extensions forum is something historically, imported from the ez.no forums, AFAIK.
I do not see any reason for closing the forums on projects.ez.no, each project has its forums so people can discuss any project-related issues over there. No need to do that on share.ez.no IMHO, as the share.ez.no forums are about eZ Publish in general.
Please keep the project-specific forums on projects.ez.no inside their project.