There is some internal debate that “Cesium is only web based”. However, my understanding of the Geospatial Content Server is that it’s just… a content server, and we can use the data in any type of application.
Can anyone confirm this possibly silly question? Can I use GCS with a native Windows app?
Welcome to the Cesium community forum Scott! Not a silly question - in general you can run CesiumJS in offline/desktop environments (usually embedded as a web view in applications like Electron that can wrap a browser in a native app).
If you’re asking if you can use the 2D imagery & 3D content from Geospatial Content Server, or from Cesium ion, in applications outside of CesiumJS, the answer is yes. Any viewer or client that supports these formats should be able these standard formats. We maintain a list of integrations here: https://cesium.com/integrations/. So for example you could load 3D Tiles from GCS/Cesium ion into STK or osgEarth, which are both native Windows applications.