Looks like it's available under the fairly permissive LGPL licence - https://doc-snapshots.qt.io/qt6-dev/licensing.html
Qt5: https://doc.qt.io/qt-5.15/qtmodules.html#gpl-licensed-addons
Qt6: https://doc.qt.io/qt-6/qtmodules.html#gpl-licensed-addons
(Source: Used to work for Nokia)
EDIT:
(Source2: https://www.qt.io/pricing)
(which is a shitty thing to do when you're not a mom&pop shop but a company like https://news.ycombinator.com/item?id=25344677)
Just like my answer to the other comment, there are a ton of "perfectly reasonable" things that one can do, that are still shitty behaviour.
That's like when someone leaves free books for anyone to take, you'd take one but never put another one for other people. You're not breaking any laws or rules. Still shitty. Especially if you have enough money to build a whole freaking library.
Like, anyone can go to a food bank charity to have a free meal. If you have a 5-digit monthly salary, that is still a very shitty thing to do, even if you and everyone else plays by the rules.
1. Could easily afford it, as you say
2. Presumably aren't releasing their software as Free and Open Source
Why? That's the whole point of LGPL, it doesn't matter how big you are, so long as your users can replace your copy of Qt with a modified copy you can use it under LGPL.
(genuine question, I'm doing a bit of market research in this area)
1) Personal License - free if <50k annual revenue
2) Startup License - keep current price (500usd/month) but
a) allow 1 month subscription commitment instead of paying 1 year upfront
b) when subscription not get extended you should still be allowed to distribute product that is not updated
c) if you payed for 1-2 years of subscriptions and cancelled subscription after 1-2+ year, you should be able to keep using the version of Qt the moment when you first signed for .
3) allow Startup to choose another licensing option. Instead of paying upfront licensing fee, just allow paying annually 5% of revenue from products that keep using Qt.