If you take a product such as think-cell at first glance it looks like an add-in. Google think-cell Fraunhofer.
However it is an actual program that has installation files and not acquired through appsource.
Question 1.How is this done? It does not seem to be using the add-in JS API.
Question 2.If I wish to develop a standalone application that can be downloaded and installed as its own separate executable, is it possible to do that using the JS API or is appsource the only way to deploy?