This is highly speculative - but I'm wondering whether you have any thoughts on the viabiliy of this idea? I'm thinking of an extension which uses jsMath to render mathML input as well as TeX input. The benefit would be plugin-free mathML capability for all browsers with the possibility of copy/paste to other mathematical applications (Mathematica, Maple - also Word/Powerpoint now). I'm imagining a component that builds your mlists from mathML.
Davide P. Cervone
Certainly making a jsMathML has been one of the goals, but has not yet materialized. It would be possible to do as you say and have it create math lists, but I'm not sure that's the way to go. If you want it to process native MathML, then the current implementation of jsMath won't work for that because MathML has to be in XML pages, and jsMath is not XML compliant. It would take a major rewrite of the internals in order to make that possible. If you want to allow MathML within standard HTML pages, then you would need to encode them in some way so that browsers don't remove the tags. Some browsers remove unknown tags from the DOM so that if MathML (for instance) appeared in regular HTML all the markup would be lost before jsMath had a chance to work with it. It might be possible to put it in CDATA or comments or strings or something, but when I originally investigated that possibility back in 2004 when I first wrote jsMath, it did not look very promising. Perhaps things are better these days than they were then.
In any case, I don't think it is a small job.