SAPUI5 is a JavaScript web application framework. It is used by SAP to create SAP Fiori apps, and others can use it to create Fiori-like apps. However, it can also be used to create apps that do not follow the Fiori Design Guidelines and are thus not Fiori-like apps. Furthermore, there is a free, open-source version called OpenUI5.
SAP Cloud Platform is a platform-as-a-service that provides many different services, including a runtime for serving HTML apps like SAPUI5/OpenUI5 ("UI5") apps.
UI5 apps are often run from an SAP NetWeaver AS ABAP system (serving as an SAP Gateway system) or from SAP Cloud Platform, but as each of these apps is simply a collection of static files, they can be run from anywhere by including an index.html file.
So yes, you can create an app that has no interaction with SAP HANA.
