This chapter shall not apply to any of the following persons or organizations: (1) The government of the state, municipalities of the state or any department or agency of the state or such municipalities; (2) the government of the United States or any of its departments or agencies; (3) any school, public or private, offering as part of a vocational education program courses and training in any aspect of home improvements; and (4) any person holding a current professional or occupational license issued pursuant to the general statutes, and any person registered pursuant to sections 25-126 to 25-137, inclusive, provided such person engages only in that work for which such person is licensed or registered.