Great idea though I am skeptical it will be adopted in contentious situations without some sort of stick. In amorphous situations where there is just high trust but an aversion to talking things out I could see this kind of tool being used. But in contentious or low trust situations (strangers) I suspect most people do not want fairness, they want to be ahead. A fair agreement will, paradoxically, disappoint everyone since every party feels the lack of clear advantage.

I think this is mostly right, but it depends a bit on how you frame "fairness".

The system isn’t trying to impose a notion of fairness from the outside. It’s trying to find agreements that both parties prefer over their BATNA (i.e. what they get if they walk away). If there’s a way for one side to come out clearly ahead given the other side’s preferences, it should find that. If not, it finds the best mutual improvement available.

On the "no stick" point, I agree this probably isn’t useful in fully adversarial situations where one side expects to win outright. Where I think it helps is when both sides suspect there’s a deal but can’t quite find it, or don’t want to go through a long negotiation process to get there.