Forgive my ignorance, but I'm a little confused on the requirements for hosting of the application. Is ArcGIS for Server required for online access or can the application be hosted through ArcGIS Online?
Jason,
It requires Arcgis for Server.
You can actually stand up the application using ArcGIS Online hosted services, so ArcGIS for Server is not required. However, you will need a web server to host the application.