I've heard somewhere that the actual mounting bit supplements the fork and takes away the risk for braking. But that's just me being hopeful cause I need a brake too and don't want to bust out for a new fork..
I can't imagine that they would sell these things unless they were street legit.. Also, since you're gonna be using it as an e-brake (likehood of locking the front wheel) wouldn't you want to make extra sure that it won't **** up your fork too?

Let's see some answers, I've searched various threads regarding this topic without any real answers..