Sure, and that's what a disclaimer, like the one you even acknowledged, does. Make it obvious that this is something that he did for fun and that you shouldn't do the same unless you know the risks.

So, going back to izacus's comment, is the preaching really necessary? He gets it, and people who read this and are in a position to act upon the information (ie. have a plane, with this GPS, and want updates) also are likely to understand the ramifications, so, really, what does the preaching add, other than negativity, as was mentioned?