It's not for lack of demand. Mitch Kapor (Agenda) and Mozilla talent tried an OSS reboot, Chandler. It was so well funded and failed so spectacularly, that there's a book about it.

https://www.amazon.com/Dreaming-Code-Programmers-Transcenden...

https://www.chandlerproject.org/vision/

> cards can not only have multiple parents but can have different parents for different users. This aspect might be novel

Very nice.