It appears you've just rec'd a very well written "shot across your bow!"
Curiosity drives me to wonder one of two things... How fast your site comes down -- or -- how fast you respond and retain your own legal counsel.
There is a great lesson here for many... Shades of grey abound eveywhere here on the internet... One person comes out with an eBook and then there are dozens of others selling basically the same text -- with just enough twist -- to defy the copyright laws.
There is a great satisfaction in seeing a response to Jimmy's request (and advertising) which carries a no-nonsense, businesslike tone.
With all of the copycatting and product-stealing which abounds in our incestuous community... I sincerely hope there are legal actions pursued -- and enforced -- if need be.
Jimmy D??? Now is the time to make a response and stand firm upon your ground. The shot has been fired. Either make amends or make your case!
These folks sound like they don't want to seek legal actions... But are very well capable of doing so!
Good luck to you Jimmy D!!! We'll be watching this with interest...