Hi again.
Your question was somewhat tempting so I did some further research.
MusicXML was initiated by "Recordare"
http://www.recordare.com/musicxml/community/software and you'll find some information about musicXML supporting software there. Some more links could be found here:
http://www.econcertband.com/software.html
I've also found a free MusicXML viewer written in Java by Richard Boulderstone
http://sites.google.com/site/richardboulderstone/home This might be interesting as he could probably create a Java applet from the Java application too that could be used in web pages. I've sent a mail request to R.B. to find out more.
Let's see if we find a solution...
...600 bucks sounds really like a lot!...
