This means they are actually an independent contractor working at the desired location. This, in my opinion, is slightly different than an individual working in private practice. Some of the positions are funded just as a secretary, physical therapist, or teacher might be funded. These monies are built into the facility's budget. Typically, however, music therapists are funded by grants and less commonly, through third-party reimbursement.
Some families are private pay, meaning they pay out of pocket for music therapy services.
Personally, I work in schools, in families' homes, and at private agencies. I am funded through grants at any private agencies. Some parents in my area have been successful in getting reimbursed for music therapy services via their county board of mental retardation and developmental disabilities. If you don't already have a music therapist at your child's school, you can be successful in obtaining music therapy services. Prelude Music Therapy has spent much time devoted to the process of getting music therapy services in public schools.