Systems and methods for installing and upgrading application packages to an application platform of an on-demand database service. In some embodiments, application packages are uploaded to a directory by developers for installation by subscribers. Some embodiments enable a developer to send identification information to a subscriber to allow that user to access and install an application package created by the developer. If the developer changes the original source package, the subscriber may pull into its organization the change(s) made by the publisher while preserving any data rows the subscriber had created since first importing the package. One or more flags may be set in the package definition to determine whether and to what extent customizations to a package may be made and upgraded by the subscriber and/or developer.