Professor Alex Halderman from Michigan has performed a few studies on Electronic Voting and Electronic Voting Machines, and essentially has proven that it is insecure. At one point, he hacked an American EVM to play the Michigan Fight song on every submission. You can read a few of his papers here: [1][2]

The challenge of creating anonymous and secure voting systems is still an area of constant research, and I do not believe that the Australian gov't has solved these problems yet.

Should we view the source? If we know it's insecure because it's basically unbelievable to think that otherwise, what good will seeing the code do? The fact that it is not being shown basically confirms the insecurity (if it was truly secure, we'd be able to see it without having a negative effect on the system). It seems the right thing to do is to fight this method of voting until EVMs are more secure, but maybe we should hedge our bets. Maybe we're going to be stuck with these EVMs in the interim, and we should avoid leaking the source to prevent people who have difficulty viewing the source.

[1] https://jhalderm.com/pub/papers/evm-ccs10.pdf [2] https://jhalderm.com/pub/papers/voting-wecsr11.pdf