For the case of charge, it seems clear that in a perfect conductor the free charge refers to the excess charge that has been dumped into the conductor, while the bound charge refers to the charge that is set up to cancel the electric field within the conductor. Please correct me if I am wrong.
For the case of current, it is harder for me to understand. How do you disentangle the two concepts?
The reason I ask this is really in order to determine what the appropriate boundary conditions should be on a conducting surface. Say if you have an electromagnetic wave hitting the surface. Should there be free or bound charge? Should there be free or bound current?