As to the license, from what I've seen it varies by state, in CA, generally
once it's registered as an RV you can drive it with a regular license. You didn't list your state, so there's no telling in your case.
For the locks, I used a normal RV lock on my side door, which is probably the same as your back door.
Needed about a 1/4" shim, the bus door is a little thinner than an RV door apparently.
On the front door as a 'down and dirty' solution, I used a couple of eye bolts and a bicycle lock. Recently I changed it to a garage door type thing which I think Lily(?), among others, showed pretty good.