Child caring institutions, and child placing agencies, family boarding homes, group care homes or foster homes, when licensed in accordance with this part, may receive needy or dependent children from their parents or legal guardians for special, temporary or continued care. The parents or guardians may sign releases or agreements giving to such institutions or agencies custody and control of the persons of such children during the period of such care, which may be extended until the children arrive at legal age, or they may surrender such children to a licensed child placing agency for purposes of adoption, such surrender to be in conformity with the provisions of the law governing the surrender of children for adoption.