Flash is not propertiary platform. Flash is a tehnology that allowed you to run apps in your browser. It didn't control what apps you are allowed to run because

Flash is not propertiary platform. Flash is a tehnology that allowed you to run apps in your browser. It didn't control what apps you are allowed to run because it is not a platform but a software. HTML5 is not near to replace Flash, and with main propertiary platform owners controlling browser market, it may never become Flash replacement.