I'm trying to make sure that this show doesn't come across as as advertisment placement on HPR I won't provide a link to our application (which wouldn't help a lot anyway as we don't really have much of a web site anyway.).

However I'll link to some of the technical components:

The Computer Algebra System we use is called Maxima, its history goes back to the early 80s. It's written in common lisp.

We have considered switching to SymPy as a more modern alternative. SymPy doesn't offer the feature completeness Maxima does, though. It has still a long way to go.

Our servers run Debian. The current version is written in PHP but we are working on a new version based on dockerized Django with a JS frontend in Ember along with some micro services written in Go, Python and PHP.

To render math we use MathJax in the current version and KaTeX in the new version. The PDF-export of worksheets is of course done in LaTeX.