Unlike Workbench in RCP where applications are standalone applications. eWorkbench ensures that the UI is shared between multiple applications through their views.
A bundle Activator is a class implementing an org.osgi.framework.BundleActivator interface for the created plug-in. Plug-ins should implement this interface if they use or provide OSGi-specific functionality. If you are using an eclipse development environment earlier than 3.4 execution environment selection is not part of the Plug-in Project creation wizard. In this case edit the Manifest.mf file of your plug-in and add the execution environments required by the plug-in in the Execution Environments pane of the Overview tab of the manifest editor. The environments are CDC-1.1/Foundation 1.1 and OSGi/Minimum 1.1.