"Despite its name, TeXmacs is not a front-end to TeX or LaTeX.[mHowever, TeXmacs documents can be converted to either TeX or LaTeX. LaTeX also can be imported (to some extent), and both import from and export to HTML, Scheme, Verbatim, and XML is provided; the HTML export is stylable with CSS (since version 1.99.14). There is a converter for MathML as well, and TeXmacs can output PDF and PostScript for printing."
Typst is Apache licensed. I install it with "cargo install --locked typst-cli". The subscription model is for their web interface with storage. I write simple worksheets for a living, so I've been using it instead of TeX lately. (I've use LaTeX or plain TeX since around 1990.)
Surely both of these characterizations depend on the person? I can believe that integral_t^oo is idiomatic if that's what you're used to, and maybe it's easier to pick up from scratch, but, for someone long used to TeX, it just makes me wonder what other unpleasant surprises someone else will have decided are actually pleasant.
A friendly person on the internet already put up the typst-to-mathml part of this [0]. I have been considering the ultimate yak-shave of building a static site generator around this...
"Despite its name, TeXmacs is not a front-end to TeX or LaTeX.[mHowever, TeXmacs documents can be converted to either TeX or LaTeX. LaTeX also can be imported (to some extent), and both import from and export to HTML, Scheme, Verbatim, and XML is provided; the HTML export is stylable with CSS (since version 1.99.14). There is a converter for MathML as well, and TeXmacs can output PDF and PostScript for printing."
[2] GNU TeXmacs:
https://en.wikipedia.org/wiki/GNU_TeXmacs