Over the past year or so many browsers, including Firefox, Opera, Chrome and Safari have got support for web fonts using the @font-face CSS property. This allows for a new font face to be defined, e.g;
src: url("fonts/jsMath-cmex10.ttf") format("truetype");
There are two major formats, TrueType and WOFF (Web open font format). WOFF is newer and currently only supported by FF 3.6 -- however Microsoft have expressed interest in the format and it is likely to become a web standard. Converting a TrueType/OpenType font => WOFF is a trivial procedure (it is just a compressed version) and the $ sfnt2woff utility can be used to perform this. It is possible to include both in a single @font-face definition (.ttf and .woff that is).
It would be nice if jsMath shipped with both the required fonts (jsMath-cm???10 and friends) and the CSS styles. Other than this very little extra logic should be required -- if the browser supports web fonts or the user already has the jsMath fonts installed the effect is the same.
See: http://en.wikipedia.org/wiki/Web_typography and http://webfonts.info/wiki/index.php?title=%40font-face_browser_support for more information.