I think the main issue is bait and switch. You start with a license, get lots of external contributors who are working for free, get ecosystem built around it for free and then change because you want to be paid.
I'm not sure how nefarious this Redis move was. I guess I was assuming any move from 'free', to 'paid', will be met with some outcry regardless of how seamless they can pull it off.
Or in other words, it is always a messy transition?