This looks nice, and I could see using it in some cases when I teach 3D functions, especially for complex functions that require more accuracy. But when introducing 3D it's often nicer to have graphs that showing gridding rather than smooth curves. For most purposes I'll probably stick to CalcPlot3D. It also has some nice features for showing points and vectors on a function, doing contour plots, and a nice surface of revolution visualization.
The project isn't exactly dead (I'm one of the maintainers). The direct-to-MathML version is somewhat dead, but the AsciiMath syntax rendered via MathJax is still widely used. The syntax is pretty mature at over 10 years old, hence the lack of commit activity.
Yeah, the original design philosophy of AsciiMath was to make that input symbol something in ASCII that looks kind of like the desired symbol. The idea of supporting Unicode as an alternative is reasonable idea and probably one we should look at (feel free to make a pull request).
One audience: undergrad students. They are familiar with calculator notation but not Tex. Particularly for simple algebraic expressions, AsciiMath is very similar to infix.
The original native AsciiMath script was limited in support, but AsciiMath via MathJax has wide browser support. We maintain the original script still, but most people use AsciiMath through MathJax.
MyOpenMath creator here. Exciting to see a us mentioned, and glad it's working well for you. BTW, the open-source software that runs it is called IMathAS, and is on Github if anyone wants to contribute :)
I've worked in OER for 5+ years. What I've been told (unofficially) by people from Creative Commons and other experts is that when using a BY-SA image in a website or text document, the license does not "bubble up" and force the website or document be BY-SA.
From my understanding, the argument is that the website or document is considered a medium for distributing the image, but is not an adaptation or derivative work of the image. If the image itself was modified, that modification would have to be BY-SA.
https://c3d.libretexts.org/CalcPlot3D/index.html