In EU it's indeed illegal and in 90% of EU countries it won't even go to court. But they can probably force you to not upgrade anything cause of licensing of the new software or if you upgrade they'll make you pay fees from that moment onwards.
But in US im pretty sure it is open for the legal battle that will cost tons of cash for both sides.
Not to be that guy, but do you have a source for this? As scummy as what they're doing is, it's also completely typical for damned near 100% of companies to reserve the right to be scummy. They all have a clause in their terms that states, 'We can do whatever we want, whenever we want, for any reason we want. If you don't like it, your only recourse is to stop using the software.'
I'd love for this to be true, but I've never seen as exclusion or other sort of work-around for EU customers in any sort of terms for this exact condition, so I'd be extremely surprised to find out it's really not allowed in the EU.
"Unfair contract terms" its pretty easy in most cases especially if its something as blant as changing price backward without acceptance of other site.
Also every country can have different interpretation (It is possible that some countries are very limited and you have to try EU level help) In some cases its even illegal to write non-competition into your contract without providing payment for the time of this being in-place ( there were tons of cases when contract was voided by that and I have even one of my contract ended on my account after single lawyer visit cause of this :] )
I would assume Unity won't even try to enforce it in EU.
But ofc. after update its over and games not yet released can most likely be forced to pay.
Probably dependant on country interpretation, but you can try make it to EU level institutions for proper help.
It seems to be pretty easy to get your contract to terminate here in Poland even in case of non-competition clausule so it would be even easier for something like retroactive price change.
they explicitly said in the contract that the terms that apply are those that were in effect at point you shipped your game
> if the Updated Terms adversely impact your rights, you may elect to continue to use any current-year versions of the Unity Software (e.g., 2018.x and 2018.y and any Long Term Supported (LTS) versions for that current-year release) according to the terms that applied just prior to the Updated Terms (the “Prior Terms”). The Updated Terms will then not apply to your use of those current-year versions unless and until you update to a subsequent year version of the Unity Software (e.g. from 2019.4 to 2020.1).
But in US im pretty sure it is open for the legal battle that will cost tons of cash for both sides.