Some years ago I embarked on a GURPS Hârn conversion at the Wikidot site. It never got quite finished. Not at all, actually ;-).
The effort will continue here. The Wiki will contain most of what is of interest.
HârnWorld and HârnMaster currently have two somewhat competing publishers (mostly on the rules front, which of course is of lesser importance for this effort – but read all about it on HârnForum): Columbia Games (the original publisher) and Kelestia Productions (the company of Hârn’s original creator, N. R. Crossby. NRC has sadly left this world for Yashain since, a victim of cancer).
The fan community surrounding HârnWorld and HârnMaster is a very active, impressive, complex and diverse “entity”. HârnForum, and the fanon publishing site Lythia.com, are great places to begin exploring the width and breadth of all things Hârnic.