I haven't asked Derek about this, but he may not be thrilled at the idea of having the ideas he sells in a book discussed on an open forum. Of course, he might not mind at all.
But, may I suggest, that you ask? Of course you do not have to, but if he would rather people not share his ideas for free, doing so may discourage him from putting out more in the future.
That would be a shame for all of us.
And if he doesn't mind, he may actually choose to look in on the thread and contribute.
Seems to me only good can come of asking.
Brad Henderson