MathJax is very flexible and its output is certainly high-quality. However, it is difficult to configure and package in my experience, and it's pretty slow.
We used it for a few years at Khan Academy before building KaTeX (https://khan.github.io/KaTeX/) which is around 50x faster to render in our experience, not even counting download size. We ran an A/B test for MathJax vs. KaTeX on the Khan Academy site and people completed measurably more exercises with the latter, even though they look identical. (KaTeX doesn't support everything MathJax does though – we still fall back to MathJax for a small fraction of our content.)
KaTeX is more likely to be useful out of the box to other developers, whereas the source of the mobile apps is not going to be a drop-in component that's useful; it'd have to be used more as a learning opportunity by interested devs. That's fine, but it's also a different market. In practical terms, the KA mobile apps also are much more KA-specific and need to be cleaned up before open-sourcing, and there's a worry that people would take the entire app and repackage it as their own (this happens all the time to open-sourced mobile apps, unfortunately). That said, open-sourcing the mobile apps is still something we want to do, so it may happen someday.
Sorry to hijack this thread and I appreciate your response.
Please keep in mind I don't ask about open sourcing the mobile apps to help other developers, rather, it's to help KA. There are lots of contributions and improvements that would be made by the community if given a chance, which would benefit everyone. Contributions would have to be managed yes, but that's something that done all the time for other projects.
We used it for a few years at Khan Academy before building KaTeX (https://khan.github.io/KaTeX/) which is around 50x faster to render in our experience, not even counting download size. We ran an A/B test for MathJax vs. KaTeX on the Khan Academy site and people completed measurably more exercises with the latter, even though they look identical. (KaTeX doesn't support everything MathJax does though – we still fall back to MathJax for a small fraction of our content.)