Q: Why is it compiled in non-secure mode?
Q: Are there any bugs that were not present in the original Mathomatic?
Q: Why not just use the server-side implementation?
Q: Is this secure?
A: Yes. None of the data that you enter is ever sent over the Internet. The page and script are downloaded entirely over HTTPS so they can not be spoofed or altered to leak your data.
Q: Should I rely on this for critical applications?
A: No. This software is experimental. Roundoffs, errors, and bugs (including bugs not present in the original, caused by the Emscripten compiler) may compromise the accuracy or validity of your results. Feel free to use this to do your math homework, but don't use it to build a car, for medical purposes, etc.