So why didn't you fork it?

And what specifically were the licensing issues? workout.lol is MIT from what I can see.

the code was indeed MIT.

The licensing issue I referred to was about the videos: many of them came from paid/licensed sources

I think the missing context here is what is meant by “fix the licensing”. Both the original project and this new one are MIT, so naively there doesn’t seem to be an issue.

just fork it?

the original project was built in javascript with a NoSQL backend (mongo).

I wanted to move to a more "new", (robust?) and maintainable stack with TypeScript and a SQL-based backend (PostgreSQL)

This makes a lot more sense and sounds like a good move for the overall health of the project.