In the beginning when you're just starting out with your online store you really don't need a business license unless your locality or community requires you to have a business license to run an online store.
During the first year or so you should be okay without having a business license for your online store until you grow the online store into a big business and need an office and warehouse for your merchandise then you would need a business license.
But I operate a small online store out of my home and have done so for 10 years now and never have had a business license for it and have had no problems.
If I grew the store larger one day and moved into a regular office away from my home then I would get a business license because then it would obviously be needed.