This extension to the dojox.charting.widget.Legend module was first developed for my session XPages: Enter The Dojo at Lotusphere 2011. It contributes three additional Dojo attributes to allow the legend to be multi-column and allow developers to add styleclasses to the icon and the text. An XPage in the application shows an example.
It was developed for XPages, but there is no reason why the Javascript file cannot be used in non-XPages or even non-Domino applications.