I'm a newbie on Atkins, so take my advice with a grain of salt
If you have time, read the Induction Basics thread up above this forum, up in the "stickies." It has so much good information!
Ketosis sounds a whole lot like ketoacidosis. Every diabetic knows about ketoacidosis, and how dangerous it is! But ketosis is completely different, no relation whatsoever to ketoacidosis. Ketosis means your body is burning fat.
So another way of phrasing the question would be, "is it dangerous for a diabetic to lose weight?" And generally, if the diabetic is over his ideal weight and has the go-ahead from his doctor to lose weight, it's not only okay, but a good thing.
Dr. Atkins started using the word lipolysis (means the same thing as ketosis) to describe fat burning, because it was less confusing for people. But most people still use the old word, because old habits die hard.
Well, other than that, I don't have much to add, because the Induction Basics thread up in the stickies answers questions a lot better than I could, but I wanted to say, welcome, I'm glad you are here, and if you do decide to try low-carbing, I wish you the best of luck in your journey to the happiest and healthiest you.
The induction part of Atkins is the lowest carb and the strictest. This is very low-carb for that period, because it is trying to allow your body to clear away the excess insulin and start from scratch metabolically. It starts your body burning fat for energy instead of burning the carbs. Because when your body is burning carbs, it's not burning fat, and that means you aren't losing the fat you want to lose. Then, you slowly add carbs back one item at a time, to give you a chance to see what foods you might be sensitive to, that might cause your weight loss to stall. You also get an idea of how many carbs you can eat each day and still lose weight and burn fat. It varies from person to person so you just kind of have to play it by ear. By the time you are in the maintenance phase of the diet, it looks pretty much exactly the way my diabetic relatives are advised to eat by their doctors - some protein and fat with every meal, and get your carbs from vegetables and some moderate amounts of complex carbs rather than white bread and cake and candy bars.
Any diet should be done under a doctors supervision, naturally. Especially when a person has any conditions like heart disease, diabetes, etc.
From what I can tell, the medical community is arguing with itself about what is healthiest. Some doctors insist that high carb, low-fat is best. Other doctors think that low-carb, with good portions of protein and fat, is best. So you never know what reaction you will get when you tell your doctor what you want to do. If you go to the official Atkins links, they have tons of studies published in medical journals that show low-carbing is good for the health and not harmful. Sometimes it's useful to print things like that out to show to the doctor.
Best of luck to you and your husband, glad you are here!

P.S. here's a link to the official Atkins site! Word of caution, after Dr. Atkins died, a company took over everything and of course companies want to make money, so they are trying to sell lots of products. Including these energy bar things. Some people like them and say they still lose weight on them, but some people find they stall the weight loss. It's just one of those individual things. But there's a whole bunch of good information at that site.
http://www.atkins.com/Homepage.aspx