> This is the same for Australian developers.
I don't see any sign of this being the case in my searching. This document (https://www.lexology.com/library/detail.aspx?g=628b5bca-b7d5...) suggests that Australia does recognize perpetual licenses ("Does the law in your jurisdiction recognise the validity of ‘perpetual’ software licences? ... Yes."). Would you provide a citation?
> For example, it is conceivable that someone who has contributed to a large project, say... Linux, has an issue with one particular corporation who have been found to acting unethically, say... Google. They can revoke the right to use their contributions to the Linux kernel by Google. They don't have to supply a reason for it.
As noted above, I'm skeptical that this right exists in Australia. But if it does, the worst that would happen is that a person's contributions would need to be removed from Linux. There are probably a handful of individuals who own the copyright to their works whose contributions would be difficult to replace, but most of them probably have sufficient economic or other incentives not to do something like what you're describing. That vast majority of new code written in Linux is written by employees of large corporations and isn't subject to this risk the same way.
> This is thus far untested in court
To say the least. It seems likely to me that courts in many jurisdictions would decide that an open source bait and switch was not what their corresponding legislatures had in mind when drafting license reversion rules. This risk seems unlikely to me, because you'd need a dev with plenty of wealth to pay lawyers, who also really hates some company beyond any practical economic extent, and also contributed a lot to Linux as a private individual. I don't know how many of that type of person you're going to find.