I would also agree, although you can never tell how many people have booked the "regular" fare already. If enough of these seats are paid for in advance then it might be possible to have enough in the kitty to pay for the day to day operation but thats a very dangerous and possibly illegal way of operating an airline. JetGreen are just a tour operator in the end.
The only way anyone will know if its a success or not is when the first aircraft arrives. There will certainly be some interesting days ahead.
