Hub Karma score is mainly related to how you link to others posts and category pages from your own posts. If you link more you will get more Hub karma score.
While you are on a hub, the 'suggested links' option on the top helps you making these links.
It seems the Hub Karma Score has a bearing on Hubber Score. However I dont think it influences the Hub score or any other thing.
Another related information: While linking to other hubs, if you use your URL tracker, there is a possible additional income from that.