Everyone here is talking about paper ballots. Good, but this ignores OP's question. Most voting machines, even if they have paper trails, have some software in them. Just saying "paper ballots" doesn't address the issue. To answer OP's question, I personally have no idea but think it should be. Much of our scientific work is open sourced (e.g. codes from national labs, NASA, etc). But I think a lot of people don't un…
The answer to OP's question is... why have software at all? Why not just paper? Why do you want a 'voting machine' at all? What's wrong with paper? The solution to a problem that should not be solved with software is not to have different software.
I agree that paper ballots are ideal, but the machines are already in use.