Once your code contains GPL code that is not yours, it has to be GPL. Particularly in v3, where a number of loopholes were closed. You are free to attach further non-conflicting clauses to it, but the GPL of the original code must be respected. That’s the entire point of the GPL.
Double-licensing requires you to have ownership of the entire codebase. At that point, you are licensing everything, so you’re free to pick any license that suits you.
You're agreeing with the OP. The point they were making was that the Australian government could've gotten the source code under an alternative license by asking the sole copyright holder (which I believe is either the Singaporean government, or a contractor of the Singaporean government).
But to be honest, as an Aussie I don't think our government is remotely competent enough to have considered the copyright license of the code they were using. There were initial reports they would provide the source code of the application, but these promises were quickly revoked for reasons of "national security" or some other such rubbish.
EDIT: I meant to say that it was a bullshit reason such as "national security", not that it was a direct quote. The actual reason they claimed was that it was easier to hack if the source code was public.
Now that 'consultation' might be a delaying tactic, but it's just as likely to be that the Dept. of Health has no idea of the implications of such release. It certainly doesn't suggest the revocation you claim.
I was basing it on the public statements of the Health Minister[1].
Now, it's very possible that they'll release it tomorrow and this whole discussion will have been a waste of time -- but at the time of writing the Minister for Government Services said unequivocally that they would release the source code[2] and later the Health Minister said they were "unsure it would be safe"[1], and finally when the app was released the source code was nowhere to be seen. To be fair, he was insistent that they would release it (despite being "unsure it would be safe").
But sure, I also wouldn't be surprised to discover that the whole process has been delayed by some other bureaucracy. After all, they probably see releasing the source code as a token gesture and not a form of review by the public.
They didn't say it was for national security ("or some other such rubbish" was the point I was making -- that it was a bullshit reason, not that it was a direct quote). The Health Minister claimed that having the source code public would make it easier to hack[1]. But it's just as ridiculous of a statement.
“The first thing we want to do is make sure that we're protecting the safety and the privacy of individuals. Everything that can be released, will be, for sure,”
I don’t share your cynicism but I do hope that “everything” means everything.
You can release you code as GPL. But you can also release you code however, separately if you want.
Also it depends on OpenTrace's libraries and if it's been contributed to.