>> This looks like an open source alternative to Mathematica/MathLab/Maple running in the browser.
Yes. If you're on Linux try out wxMaxima as a local app. I'm not sure how to get the Windows version of wxMaxima since you end up in some weird sourceforge hell trying to get an installer.
Perhaps because it has such a long history and because this was published in a Lisp website, Maxima was considered known.