That's a good question. The S-expressions are actually a trivial part of the project right now, because there is no symbolic computation going on, just composin

That's a good question. The S-expressions are actually a trivial part of the project right now, because there is no symbolic computation going on, just composing S-expressions without any form of rewriting and then generating the website from the final S-expressions. So there is wheel reinvention, but it's just a few minutes of work :) Python happens to be convenient for the website generation, plus I use it because I have other tools in Python. The code is a bit of a mess right now, but I will clean it up gradually. Later on I plan to make the formula database itself available in some language-agnostic form, with the idea that you could interface it from any programming language or computer algebra system you like. Both Python and Julia are on my radar. And Racket would be quite nice too, since I agree that it's a very nice language for this kind of thing!