Is there some sort of copyright preventing manufacturers from selling these diy batteries online or in stores?
Not at all. Though if I am going to be honest this one is a tricky one for me to fully understand. On one hand we have the people who tell me what I am doing here is nothing new, no big deal, the kind of stuff we learn in school. Then on the other hand we have the people are blown away by this. Like me! So, I am unclear why, if indeed this is something we learn at school (must have been daydreaming in that lesson!) why 90% of people fall into the second camp. Was everyone daydreaming in that lesson????
As you say I think this is largely to do with the withholding of information. In the media particularly. Just keeping our attention anywhere but here. So while we may have been taught this in school (as a galvanic cell) the implications of what this really means have been kept from us.
Chatting with a friend today he tells me it will be the screws which 'die' first. But not because they dissolve. Rather because the layer of zinc they have on their surface will be depleted. He was unsure how long this would take however so let's see what happens...
P.S.
However, in order to turn a particularly gentle technology for a few into an equally gentle one for many, mass deployment has always been the solution. Now, however, it is precisely mass use that is the problem again, and one notices that one is going round in circles. Nuclear energy is a reliable source of energy for many contemporaries, but the opponents and the fear of it have just as many comrades in arms. Therefore, no energy, no matter how it is obtained, will satisfy anyone in the long run.
Those who live to save either themselves or others or "the world" ultimately live on the premise of fear. He who is without fear lives more easily.