A license issued under chapter two shall be valid only for activities conducted under the name of the person or organization to whom such license was issued or under the trade name stated in the application therefor; if a licensed activity is to be conducted under a trade name, the application must state that trade name. No license shall be issued for more than one trade name, and no licensed activity may be carried out under more than one such name; provided, however, that if a person or organization was engaged in bona fide licensed activities under more than one such trade name or was issued a license to conduct licensed activities under more than one trade name prior to June fifth, nineteen hundred seventy-three, a single license shall be issued for such trade names. Licensees shall notify the commissioner or the commissioner's designee of any change of trade name at least ten days before such change becomes effective, and no such change may take place without the prior written approval of the commissioner or the commissioner's designee.