To run the demo program, open a terminal, cd to this folder and type the command
It will give you the choice of which of the dialog-providing demos to run. Each of these are in fact standalone yabasic apps themselves and can be run the same way.
NOTICE: Yabasic has a bug ATM where it will crash any script or menu you try to launch a yabasic app from (at least in Linux). I have reported this, but for now the main demo.bas program is nonfunctional. One way around the problem is to go back to an old 2.79.x version of yabasic, for example my homemade deb here.