I am currently working on recreating this in my free time, as a fun project.
I am addressing Windows platform first and am using DirectShow. I am making great progress as seen here - https://github.com/Noitidart/ostypes_playground/commits/audio-capture
If anyone is want to collaborate, especially on the Linux and Mac part, please let me know. I would really appreciate it. Even if you don't want to get involved in the js-ctypes, if you know the AVFoundation on Mac, or the method on Linux, if you can show me the code I can port it.
I know of the future of WebRTC however, I have seen many extensions in Google Chrome do this and they had to rely on binary components to get it perfect. This is why I'm going with js-ctypes approach.
Please email me at firstname.lastname@example.org and I would love to work with you!