The JavaConfig source tree contains Eclipse project metadata (.classpath and .project files), making it convienient to import. Also, as Ivy is used to resolve dependencies, it is necessary to set up an IVY_CACHE variable as detailed below.

From within Eclipse:
1. Preferences->Java->Build Path->Classpath Variables->New...
   Name:  IVY_CACHE
   Value: [your-javaconfig-root]>/ivy-cache/repository
2. File->Import->Existing Projects into Workspace
3. Select [your-javaconfig-root]/org.springframework.config.java/
4. org.springframework.config.java should show up with a checkbox
            

The project should now be imported, error-free and ready for development.