Curio can currently only export and import mind maps via the Outline Processor Markup
Language or OPML. OPML is a flexible (some say loosely-specified) XML schema designed
for recording outlines. It therefore carries only a subset of the information required for
mindmaps.
I have no information on the Curio format itself.
Anyone making an XSLT for conversion from OPML to other software is invited to submit it
for inclusion here for general use.