I wouldn't say Mozilla has reached this stage of fraud or exploitation directly yet (to my knowledge), but the decisions they make consistently indicate they are on the path to that level of corruption and enshittification, and history has taught us there are zero guardrails in place to effectively prevent it.
In the Reddit example I gave, the crime is essentially a form of "bait-and-switch", false advertising, or charity fraud; scamming volunteers into donating their time and labor to build a product under deceptive and misleading pretences then, once achieving a certain threshold of success, changing the value proposition to a state where they would not have donated their time or labor to begin with. The same applies to an open source product which switches to closed-source. When you change the value proposition on volunteers like that, you have transformed their time and labor from a donation to unpaid wages, as they literally built your product and company for free, and are the reason your product exists at all. If you do not pay them out or backpay them in some way, or you can't, you are no different to any other white collar ciminal scammer, exploiting charity for profit.
Allowing this type of fraud to succeed, and become an accepted business practice, is socially corrosive and destructive. It's a strong indicator of corruption to the rule of law in the legal, political, and economic system.