There is a great debate over this but my overall feelings is if there is a slight chance it could be rancid, I would avoid and I never, never ever cook with them. But dehydration is such a low temp, that I might think we can reconsider. I also tell people to avoid all products containing flax such as butter. Just my opinion. I did post an article for you to see.
Too many people are taking advantage of one small thing and running with it. So alot of press about the benefits of flax. Many are also stating to grind and store it for one month, this is completely wrong. You grind what you will use within ten minutes only. Keep all seeds in the frig. I am an expert on flax as you might know as I am a budwig advocate. See many post on the flax forum.