Requirements seem to vary, depending on where you live, or your business is located.
When I lived in Virginia DJs weren't required to obtain business licenses. We were in the same class as Boy Scout groups, etc.
In Delaware, DJ companies are supposed to have a state biz license. If you live within the city or town limits, or your business location is there you're supposed to have a city biz license as well.
Last I heard, anyone may obtain a Delaware biz license, anywhere in the country. You don't have to live here nor does your company have to be located here.