Under the DMCA anyone breaking a digital lock, no matter how trivial it is, has broken the law, regardless of whether the sell their results.
For a good example of how it has been abused in the past, look up Lexmark and how they tried to use crypto code to lock out competitors from providing third-party ink refills. I'm not sure what the eventual outcome was there.
My understanding is that the law, created in the Internet's infancy, is meant to protect and prevent direct copyright infringment.
Can anyone explain why they're allowed to (seemingly) abuse this act? They're not selling pirated copies of the tractor control software?