1. A computer program product, comprising a non-transitory computer usable medium having a computer readable program code embodied therein, the computer readable program code adapted to be executed to implement a method, the method comprising: creating, by a first user of an on-demand database service, a package, defining at least an application, that references a set of one or more metadata objects, wherein the package includes: profile information defining at least one group of users allowed to access the application, user interface information defining a customization to a user interface, and a flag set to indicate that customization of the one or more metadata objects is allowed; editing the package; verifying automatically the package; and exporting the package for use by a second user of the on-demand database service, wherein the package including the customization to the user interface is accessible to the second user when the user is included in the group of users allowed to access the application; wherein the verifying occurs prior to installation of the application; wherein the package includes at least one of an object, a field, and a relationship.