This chapter shall not apply to income received from the department of social and health services for the cost of care, maintenance, support, and training of persons with developmental disabilities at nonprofit group training homes as defined by chapter 71A.22 RCW or to the business activities of nonprofit organizations from the operation of sheltered workshops. For the purposes of this section, "the operation of sheltered workshops" means performance of business activities of any kind on or off the premises of such nonprofit organizations which are performed for the primary purpose of (1) providing gainful employment or rehabilitation services to persons with disabilities as an interim step in the rehabilitation process for those who cannot be readily absorbed in the competitive labor market or during such time as employment opportunities for them in the competitive labor market do not exist; or (2) providing evaluation and work adjustment services for persons with disabilities.