It matters where you live, but the license categories are a vehicle mass and capacity issue, typically (axle or wheel numbers are mass/load-related). You have to look at the license classes in your jurisdiction and see. I am sure there is a website made by the government where that info will be laid out.
People usually do not need a special license to drive a long RV, so it is likely that if your vehicle is not meant to carry its load of passengers (it does not have the seating capacity), it will not require a special class of license. But look at the laws and see. I believe that, at least where I live, it is not the actual number of passengers at any given time, but the design capacity which matters (the available seating). If you take out the seats, it does not have the capacity and thus is not categorized specially. It becomes a basic box van or box truck.