The rest is plugins, which anyone can write or modify. There's no need for the plugins to get merged upstream - just use them in your project, and share them publicly if you want. You could even do the same with the pre-pro versions of the pro plugins - just make the (likely minor) modifications to make them compatible with the current datastar core.
They're also going to be releasing a formal public plugin api in the next release. Presumably it'll be even easier to do all of this then.
This is nonsensical. Someone did something for free. Fantastic. They used it, successfully, for a production system that enables scheduling for their job.
Nobody took that away from them. They didn't force them to rebuild their tool.
The code is even there, in the git history, available for them.
If OP doesn't like what the devs decided to do with the project, just move on or fork and pay someone to help you fix any outstanding bugs or missing features.
The modern one is what op and lots of younger generation agree upon. It should always be open source and continue to be supported by the community.
The old folks are basically take it or leave it. Fork it into my own while taking the maintenance burden too.