nteract is an Electron app that runs on your desktop, which means that some code is intended to run in a main thread (native macOS menus, etc.) while the rest goes in rendering threads (browser).
In Electron, GUI-related modules (such as dialog, menu etc.) are only available in the main process, not in the renderer process.
Here in src/, there are two primary components:
main/- the main thread and boot up code for all notebook windowsnotebook/- all the UI goodness of the notebook, intended for a single window