The worker doing her homestudy, in her home state will be a lic. sw. That doesnt mean the CHILD's worker will be. But i call everyone a "sw" regardless just for shorthand.
There is a difference in adoption homestudies and foster care homestudies though arent there? The person who comes out to clear your house for fostering, measure your bedrooms, ask you questions....does s/he have to be a lic. social worker? I know that most people dealing with the adoption side of things will likely have at least a BSW.
In my state, all workers for children who are part of the formal child welfare system (ie. CPS investigations, ongoing workers, foster care licensers, and adoption workers) have to be licensed social workers. Caseworkers here work frequently for agencies that offer services that support the family in other ways...ie. parent educators, mentors, etc. I've had limited experience with ICPC cases, but all of those workers were licensed. I don't know the criteria in all states though obviously and suspect there is variation. I'm pretty sure when it comes to foster/adoption licensing, you must be licensed. For international adoption, it is definitely a must.