As far as I know HITH is something that generally is only seen in Cichlids. What you have there isn't HITH, its just where he ran into something, or one of the other fish in the tank decided to take a peice outta him. No HITH is not contagious.
And in Gouramis, and Lungfish, and Tangs, and even some catfish. It is not limited to Cichlids at all, it is just commonest in several of the medium to large Cichlids.
It is most likely partly dietary and partly environmental.
In my opinion it could be HITH or it could be a battle wound as mentioned. Do some research on HITH, and look at the pictures. I have seen gourami's with HITH, but it is a bit rare.
Dave