Do you mean the test maze? If so that is just for testing your Fake 3D tileset and is not intended to be used... But I included the source code for it in the folder DungeonViewSource its written in BlitzMaxNG which is a very easy to use language(and is free) and should translate across to any other language easy enough. In that there is a function at line 287 that generates the maze which you can modify to your hearts content. The main variable that holds the maze data is grid[X,Y] with that you could literally create your own maze digit by digit.
And you are quite free to use the DungeonViewSource as you see fit(even expanding it into a full game)
I assume you mean in the Source code? edit the code found in DungeonViewSource/DungeonView.bmx(The code is written in BlitzMax but will still open in notepad if you just want to view it or translate it to another language) You could always join the discord if you have any more questions https://discord.gg/xWcreuP