Then I suggest that you contact them and ask them directly.
Letter to Walter Martin's family:
I discovered a site on the internet that has the entire book Kingdom of the Cults posted. I suspect this is in violation of copyrights and if left alone could impact the revenues for the Estate of Dr. Martin.
Here is the link:
http://www.biblecentre.net/cults/koc/contents.htm
I would appreciate it if you could let me know if this is in violation of any copyrights owned by the estate or if they have permission to publish it.
Thanks