Despite the sensationalistic title to the article. there is some validity to the study. No, reading from an iPad at night is not "killing you", and the Huffington Post should be ashamed of themselves for putting it that way, and in the process spending some of the credibility.
It has been well-documented that the human body has diurnal rhythms that are affected by cycles of light and dark (day and night), and that affect sleep. That is why light therapy has been used with some success in overcoming jet lag for those traveling over many time zones.
Exposing oneself to a long period of light just before bedtime--from an iPad or anything else--could well affect one's diurnal rhythms and sleep cycle timing. An iPad up close produces a fairly immersive bright light, much more than normal room lighting at night. In the study they exposed the subjects for FOUR HOURS each evening. That was a bit extreme compared to what one is likely to do in normal, everyday use. That is more like light therapy than normal iPad use. Exposure for an hour or so before bedtime would have much less effect, but may still cause some sleeplessness for some people. Note that I said "some" people--not everyone is affected, nor affected to the same degree.
Bottom line, ignore the sensationalistic title of the article. Instead, take this tidbit of information from it: IF you have trouble sleeping at night, and IF you use an iPad or other illuminated device for awhile at bedtime, try discontinuing its use for awhile and see if the situation improves. If you don't seem to be affected by reading on an iPad in the evenings, then don't worry yourself about it.
One thing is for sure, you're NOT going to die from it!