ghans wrote:I suppose you don't need a real desktop to start a Gambas app in fullscreen....
...well, I did say it was a simplified answer.
If you want to run a Gambas GUI app you would need a windowing system and you would also need a widget toolkit (e.g. either GTK or Qt). So you might as well run a light-weight desktop, unless you want the system to be up and running very quickly. Then ncurses is probably the way to go, as your app could be running on a Raspbian Pi in about 15-20s (maybe less using Arch Linux).
A few years ago I created a Thin Client using Gambas on Lubuntu running LXDE for a local school. The students could only see and interact with the Gambas screen (unless they knew the admin password). So that is another possibility. Or maybe look at one of the Pi "Kiosk" systems.