I know I've posted this before but its a bit hidden and I found a more convenient place to download.
The FSI material is produced by the government of United States of America and therefore is in public domain. You can download the whole course (both books with audio) here:
http://www.freelanguagecourses.com/category/korean/ , (320MB)
They're very thorough and highly recommended, and also go well with KClass101.
If you want to have a look at the legal stuff go to http://www.fsi-language-courses.com/ and navigate to forums. Look around you'll find it.
Enjoy!