How difficult to integrate this project with TeXmacs?

[gtusr]

There is already a Jupyter plugin for TeXmacs.

The quality of the typesetting in TeXmacs far exceeds the default equation rendering in WLJS Notebook. But TeXmacs does not offer an official web-based interface yet. Progress is already underway though in the Morgan fork of TeXmacs.

[JerryI]

Great stuff! Most benefits of WLJS Notebook compared to others stems from the fact of running in a browser together with Javascript, which renders most things and stands for dynamics.

Therefore I believe a useful integration can be done only if TeXmacs runs on web. For that there is REST API implemented, which allows to make "your own small frontend" using basic HTTP requests. (One of the developer is using now this API to add live wolfram cells to Obsidian notebook)

However, may be for your applications it will be much easies just to pair up TeXmacs and Wolfram Engine in the way how it was done in VSCode extension. It uses latex rendering of the outputs and rasterizes all plots by the default.