It might be best to ask this question on the
RPG Toolkit questions forum.
I'm not really sure how to answer your question, aside from the fact that you are only granted a license for anything that you own rights to or have permission to use. So my guess would be to ask for permission if you are using audio resources that are not yours. (If you cannot get in touch with the author, or don't know who the author is, then simply find another audio track to replace those resources you don't have expressed permission to use.) =]