Yeah I don't understand why people are acting so hurt by this. If you want to be paid for something, don't make it open source. If you want to force users to keep the source open, make it GPL/AGPL/whatever. If you want to prevent commercial use, use an appropriate license. This company didn't do any wrong from my limited knowledge of this thread.
Sure it would be great for them to give back, and they absolutely should, but I don't see why they deserve any hate (unless they hide what they did or engage in otherwise shady practices, but based on the comments I'm not seeing that).
I think you have to try to avoid the situations you described, but I think 99% of the time, bad mouthing someone who is toxic is not going to have these far-reaching negative effects. I have done it in many exit interviews and its never bitten me. I obviously do not ask for references from terrible managers who I bad-mouth in exit interviews, rather I ask for references from strong leaders who I can honestly speak glowingly about and who I develop close relationships with. I think you shouldn't be afraid to speak the truth in most cases and if you've developed a reputation as a good employee who others like to work with, many times the information you provide will be taken seriously. It probably won't be acted upon unless others report the same thing, but I still find it worthwhile. It at least gives them the opportunity to do the right thing.
My daughter is only 1, and has gone to daycare through the entire pandemic, but I can say with near certainty that if she was a few years older, I would rather hire a nanny to take her to the park everyday rather than put her in a virtual kindergarten class. It sounds absolutely awful and pointless. I don't see how a child could learn anything from it.
Sure it would be great for them to give back, and they absolutely should, but I don't see why they deserve any hate (unless they hide what they did or engage in otherwise shady practices, but based on the comments I'm not seeing that).