At the XCSoar projectm, someone has actually managed to compile a kernel with host mode:
http://forum.xcsoar.org/viewtopic.php?f=3&t=1167
http://vimeo.com/68476162
I'm sure you can get the sources from him/her.
But I don't know whether linux supports these dongles out-of-the-box so you might still need to compile a kernel module with the driver.
edit: project page:
http://max.kellermann.name/projects/xcsoar/kobo.html, contains an installer but no sources