I actually was just reading up on it yesterday because I've rooted a commercial e-ink word processor and was trying to sort out how much about the process I can legally share. The sibling post has the link to the LoC rulemakings that define the exemption categories. These exemptions are the same basis for any phone jailbreak, which makes me suspect it could be legal to publish methods as well as do it your self, but I'm still unsure.