I have grown cynical over the years with these kinds of open source challengers as it seems to be a playbook these days to bait and switch, going from a) freely license a competitor to b) build a large user base to c) switch license to consolidate power over the software, make money and slowly kill it.
Of course what's once open source will always stay that way, but if you're large enough when you branch, your engineering resources alone might be enough to turn people off the OSS fork.