When installing an archive, a "source.properties" file is saved in the directory that contains all the information from the source (Source URL, package attributes, archive attributes.) When loading local packages, these properties are used to recreate the local package attributes if present. This is also used to indentify local extra packages.
Using the Eclipse projects for ddmuilib. ddmuilib requires SWT to compile. SWT is available in the depot under prebuild/<platform>/swt Because the build path cannot contain relative path that are not inside the project directory, the .classpath file references a user library called ANDROID_SWT. In order to compile the project, make a user library called ANDROID_SWT containing the jar available at prebuild/<platform>/swt.