You don't need the home improvement license to get insurance. You very well may need a business license for the insurance company to consider insuring you. In CT you also have to pay the annual business entity fee which I think is $250 and a $10/year registration fee.
I found getting insurance the hardest part. It seemed that all of the insurance companies wanted a minimum of 3 years of experience and claims history before even considering insuring me. Maybe I just called the wrong companies...dunno. National Grange Mutual took me but it wasn't cheap. I have Peerless through an independent agent now.