Taravangian doesn't even have to try to get Dalinar to break the terms. It's 'a contest of champions to the death', which would mean that if no one kills anyone, no one wins. The terms of the contract are 'If I [Dalinar] win that contest, you [Odium] will remain bound to the system', and 'If I [Odium] win... I remain bound to this system.'
So if no one wins, if neither champion dies, is Odium no longer bound to the Rosharan system?