i am not sure what the question is i guess. i am 99% certain you don't have to register with the SOS unless you choose to form an LLC or register a trade name. i know plenty of people who run businesses and have never done either. however, i guess that doesn't mean it isn't required and nobody cares.
on the other hand, plenty of municipalities require you to get a business license for various reasons. however, i think its only for certain types of businesses and its dependent on the town. i can tell you this... have no business license in my town for any of the 3 "businesses" i operate and nobody has ever said a thing. however, i do have an LLC and trade name registered with the SOS for each. but, that wasn't always the case. again... nobody ever said a thing.
one caveat would be if you have employees or are likely to have to issue 1099s to anyone. then i think you would want an Employee Identification Number. that requires registering with the state and the feds.