Appendix A of the Sliver User's Manual provides a list of other free software programs that support parallel coordinate plots and are worth investigating. I specifically recommend having a look at Mondrian at
http://www.theusrus.de/Mondrian/ for extremely large datasets of up to a million records, which Sliver simply can't handle.
The Appendix lists the similarities and differences between these other programs and Sliver. There are indeed significant differences in features I find noteworthy, which was ultimately the impetus for me to create Sliver.
Ron
