This is a great tool for XML work, particularly if you need to deal with XSLT. I'm not in any way involved with synchrosoft, but found the cost for this to be more than offset by the timesavings I've seen.
Sure, it's not opensource, but sometimes you get what you pay for.
This is not a Java app...
I'm not sure what the comments are directed about, but the AIM client provided by AOL is an actual Linux binary, not a Java app.