Is the resources plug-in (org.eclipse.core.resources) considered part of the Rich Client Platform?
No. The workspace resource model provided by the org.eclipse.core.resources plug-in is not considered part of the Rich Client Platform. While this is the underlying data model for the Eclipse IDE, the RCP makes no assumptions about the underlying data model of the application being built. The data model could just as well be files in the local filesystem, a remote database, an RDF data store, or anything else. If it makes sense for the application, org.eclipse.core.resources can be included and used as the application’s data model, but this is not required. Much effort was put into Eclipse 3.0 to remove the dependencies on org.eclipse.core.resources from the generic workbench. Any resource dependencies (for example, the New Project, Folder and File wizards, and the Resource Navigator, Tasks and Problems views), were considered IDE-specific and factored out into the IDE plugin (org.eclipse.ui.ide).