Options for rendering musicXML "in the browser"

commercial closed source "embeddable" options:

musescore.com (one pro license for whatever you want, $60/yr)

soundslice.com "$0.50/user/month" or "$50/month for free music websites" (when I checked)

open source:

abcweb: http://wim.vree.org/js/

vexflow itself doesn't "do" musicxml but here mentions some forks of it that do/might.

related: list on stackoverflow

http://www.musicxml.com/software/ (though hard to search through all the options and they don't seem to have much more than is listed here)

You can, of course, generate pdf's and put those (or "thumbnail images of them") on your website, as well. Or record youtube play throughs of pieces.