4
I don't recall specifically seeing something for Geeklog, however the following dev project is not related to converting GL, but does appear to have scripts for importing users, forums, etc from other systems, perhaps this could put you on the right tracks if you were to migrate and do something yourself.
http://dev.xoops.org/modules/xfmod/project/?uniconvert
Sorry I couldn't be of any further help.
Kind Regards.
Tom
http://bassmanthemes.com
http://www.xoopslance.com