If by drug free you mean therapy where drugs are not given as part of your counseling, then I would like to add that a lot of T treat DID with out medicine being involved... medication is thought to slow the process of integration of alters, therefore, many T proceed with DID treatment drug free.

FYI - drugs may however be used for depression if you are suffering from it and DID at the same time, but then again that is up to you.