They can't change that without negotiating new contract. That would require giving something to get something in return. Only thing they can do is to do just the minimum. This is the current issue. They are moving towards the bare minimum.
I like opensource, I myself am a Linux user. I just like a world where perhaps individual devs can build nifty useful software that we pay a small fee for and use. This way the small guys can benefit. Unfortunately, the current state of OSS (which has changes since the early days) are concentrating more power in the hands of a few organizations.
Take Sublime Text for example. I like it that an engineer builds something useful, ask a one time fee for it and we pay something really affordable for it (while there was also a free version available). This way, talented software engineers could actually make a decent living without everyone has to build crappy software for an advert-based economy. So, IMHO, opensourcing the software is an act of grace and would be at the discretion of those engineers. To expect everything to be FOSS or perhaps even demand that, I find is detrimental for individual software engineers/small players.
Qt Company is also a 300+ employee company with 8-digit revenue. They are not some small shop trying to survive, they are a corporation that over-promised growth to their shareholders and now is trying to squeeze rules that have existed for 20 years to turn some part of the open-source ecosystem into paying customers, threatening to risk the entire open ecosystem around it for this, which includes many small shops and individuals.