How is this different from LaunchDarkly?
There's room for more than one player in the market here, it's a super important sort of tool where the open source versions are all pretty mediocre. OSS solutions tend to be statically configured, which non-engineers don't tend to have access or ability to configure. That's not to say you couldn't OSS something here, but it'd be a real effort to host.
what are the open-source alternatives, if you don't mind me asking?
Unleash is very powerful.