It seems likely that the founders will eventually stop working for Manifold. Either the platform does well and some of them sell out, or it does poorly and some of them quit. Either way, unless multiple leave simultaneously, there will be one who's last. This market resolves to that person. (Or a tie, if more than one leaves simultaneously.)

Specifically, this means them ceasing to be an owner and/or employee of the company. If they sell their equity but keep working there, doesn't count. If they stop working there but keep their equity, also doesn't count. They must be fully out.