Explanation - Namespaces are not used in unmanaged packages. In fact, even if your organization is namespace, the namespace is removed from all components when it is uploaded as an unmanaged package.
https://developer.salesforce.com/page/An_Introduction_to_Packaging
Once the components are installed from an unmanaged package, the components can be edited in the organization they are installed in. The developer who created and uploaded the unmanaged package has no control over the installed components, and can't change or upgrade them. https://help.salesforce.com/apex/HTViewHelpDoc?id=sharing_apps.htm