When your product entered mainstream with integration that would yield millions when virtually obliged to get a license is typically what happens.
When backed by a company there is an ethical obligation to keep, at least maintenance. Of course legally they can do what they wish. It isn't unfair to call it bad practice.
There is no ethical obligation. You just want them to release new work under open source licence.
That's your first mistake. Thinking any company truly gives a shit about ethics when it negatively impacts what it is they actually want to do.
> When backed by a company there is an ethical obligation to keep, at least maintenance.
You're saying that a commercial company has an ethical obligation to do work for you in future, for free? That doesn't follow from any workable ethical system.
There's no way that maintaining something is an ethical obligation, regardless of popularity. There is only legal obligation, for commercial products.