1. An application management system for managing a plurality of applications installed in an image processing device, comprising: a start instruction reception unit for receiving an instruction of execution start of the applications; an application execution unit for executing the application whose instruction of execution start has been received by the start instruction reception unit; and a warning screen output unit for outputting a warning screen about the application execution start, wherein in the case where the start instruction reception unit receives an instruction of execution start for a first application, if the application execution unit has already executed an incompatible application that would cause an unintended operation of the first application if concurrently executed with the first application, the application execution unit does not start the first application execution and the warning screen output unit outputs a warning screen about the first application execution start.