This site is now just used for experimenting with various things.
You may be looking for a live host of the latexcgi server, please use https://texlive.net
The sources for the latexcgi server are on github at https://github.com/davidcarlisle/latexcgi with documentation on github-pages at https://davidcarlisle.github.io/latexcgi/
I may in the end move that github pages site to this custom domain.