Are those dependencies also added as dependencies to your ejb/war project pom.xml?
Can you try creating a project using the multi-javaee6-archetype from http://open-archetypes.github.com/maven-repo/snapshots/ and study how dependencies are handled.
In Eclipse, first add the Open Archetypes catalog :
* On the Archetypes Preferences page (Window > Preferences > Maven > Archetypes), click on the "Add Remote Catalog..." button
* Catalog file : http://open-archetypes.github.com/maven-repo/snapshots/
* Description : Open Archetypes (Snapshots)
* Click OK to close the dialog
* Click OK to close the preferences
Now you can create a new project, using the Maven wizard :
* Create a new Maven project
* Click Next to land on the Archetype page
* Select the Open Archetypes (Snapshots) catalog
* Check the "Include Snapshots" button
* Select multi-javaee6-archetype and click Next
* Enter the Group Id, Artifact Id and Version informations.
The generated project has a dependency on commons-lang3, which will end up in the ear lib/ directory.
The ear declares (i.e provides) a dependency on logback, which brings the slf4j-api transitively, so other projects depending on that api will use the provided scope.
As for the null archetype issue, I need to look into it.