Hi David -
It would be nice if you could add a glossary or something along those lines to define the very specialized terms that are used to describe various aspects of a chart.
Its probably hard to believe since you have been working for so long on this that the general scientific public may not know the precise definition for many charting terms such as domain, range, crosshairs, markers, etc. We certainly have a good idea about these, but sometimes we work in such narrow fields that these same objects have taken on other names. Only those intimately involved in the creation of these charts are fluent in the full set of technical terms that describe the various aspects and behaviors of a chart.
A graphical depiction entitled "Anatomy of a Chart" would be a great place to start!
I'm having a lot of fun working with JFreeChart - thanks for your very hard work.