it might be difficult to ask Mr Janko himself, he died in 1919…
But if you want to find out the layout of the Janko keyboard you can have a look at this link:
In short, it is built like two rows with whole notes, the third row repeating the second row, the fourth row (sometimes there exist keyboards with four rows) repeating the second row. The big pro of that layout is that you can play each key in exactly the same way.
You can actually buy accordions with that layout on this site:
I’ve been considering for quite a long time to buy one and re-construct the right side as a melodica, but I have enough to do with refining my Vibrandoneon and didn’t want to get off course.