It's nice to see the progress being made regarding Arcturus over the past years and it really doesn't matter if it will be a closed source, you're the one programming it and people should not complain about that.
Just like you said, if you want open-source, fix it or build your own.
You've...
https://devbest.com/threads/how-to-set-up-a-retro-in-2021-iis-nitro-html5-part-2.92533/
Scroll down until you find the tutorial about the Nitro Converter.