What stops someone from viewing that repo over Tor, on a different git server, or at a public library, unsecured WiFi network, etc and being considered tainted? At what point is someone considered untainted?
This seems like a grey area that slows the pace of R&D in countries that believe code is copyrightable & patentable (the US and select Western countries) compared to say New Zealand & China, where these aren't an issue.
Where did you get that idea about New Zealand copyright? Code is copyrightable here, see e.g. [1] or [2].
And it's not about belief, but definition. Copyright and patents are human inventions defined by countries' laws (which is why different countries have different rules: different definitions). In NZ, as in many countries, "Computer software follows the rules for literary work" ([2] again).
It was more that we clarified what was and wasn't patentable, as I don't think software was exactly patentable before that either; its patentability and the ability to enforce said patents were ambiguous. Patents on software are not quite completely banned, either, as, from your link's linked source, "Processes will still be patentable if the computer program is merely a way of implementing a patentable process."
This seems like a grey area that slows the pace of R&D in countries that believe code is copyrightable & patentable (the US and select Western countries) compared to say New Zealand & China, where these aren't an issue.