[BRX]

I don't get what's the use case for SVG.
Displaying .ABC or .MSCZ (MuseScore) or MusicXML would make sense for me.
It might be interesting to take a look at http://www.seescore.co.uk

Well, SVG is the way the aforementioned developers choose to display the graphical score from the ABC or MXML files. Do you know EasyABC?
It's a WYSIWYG Editor for ABC files (essentially a wrapper for the ABC utilities) and has a score window which can also used as Viewer for ABC files.
Essentially the sheet is continually generated as SVG from the ABC input and displayed in the score window.

I don't know how these ABC utilties fit into Mike's architecture, but essentially they are doing the same (and more and probably better) as SeeScore and are free to use AFAIK.

I suggested SVG because I wanted to use my generated SVG files in MSP without the additional step to convert them to PDF. Also I thought if Mike is trying to do something with 
these ABC utilities SVG support is needed in MSP anyway.