On-demand delivery of applications to virtual desktops

A service provider system may include an application fulfillment platform that delivers desktop applications on demand to desktops on physical computing devices or virtual desktop instances. The applications may be selected for delivery from a catalog of applications, and may be required to be installed on the destination computing resource instance, or may be assigned to a customer's end user on whose behalf the resource instance was provisioned. A workflow for deploying a selected application may invoke services implemented on the platform. The desktop application may be delivered as a virtualized application package that is subsequently executed by a runtime engine installed on the end user's resource instance, without installing the selected application itself on the computing resource instance. A customer's IT administrators may create and populate the catalog, add customer-generated or customer-licensed applications, assign applications to users, apply constraints on application use, and monitor application usage.