It's commission free because anyone can make an offer and if someone else accepts it, then the two have a bet against one another with the house not taking any of it.
What seems like high juice is just the default state when nobody has any offers up. If you want to bet on a side with no juice, just put in an offer and see if someone snaps it up. It's easy to do...just do it like you're placing a bet, but before you hit confirm just adjust the odds up to the level you want. Then you will have an offer automatically put in at that price. It will show on the main screen within about 5 seconds.
It's strange so few people use the exchange...must be a trust issue or just bad marketing, who knows!?