I just want to highlight a couple of minor inaccuracies in this thread.
But using the browser's "download" or "offline" functions for Snap! are the recommended way to get offline access working.
- Downloading the Snap! source bundle works for 99% of Snap! tasks, but browsers limit some functionality like the camera and microphone access to websites which are served from an actual server. In this mode you simply click on snap.html to open and run it in a browser, and that works fine. Some folks create "Run Snap!" shortcuts and put them on the desktop, or some other easy place for students when doing this.
- If you do decide to run Snap! from a localhost server, it is still possible to access the "public" or main Snap!cloud. (And you can do this without running your own version of the cloud server -- which is a separate, but more involved possibility.)
Using the download source method might be easiest if you need or want to distribute something like flash drives that are pre-setup for a project. Or you are going to be 100% working in an offline environment.