Gordon Mohr suggested in a comment that as a name Dominant Assurance Contract is no good and perhaps “refund bonus” would be better. That may be right, though “refund bonus” seems to only describe part of the arrangement.
I conducted a brief search for alternatives, unsatisfactory apart from discovering that the term reverse bounty was recently (April) used to describe an offer by a programmer to develop a feature when a certain amount of money is raised (a bounty is offered by someone requesting a feature). At least one reverse bounty successfully raised the amount requested. I cannot tell what happens to contributed funds in the case where the amount requested is not raised. Notably for the successful reverse bounty the developer said they would ‘top up’ the money and ensure the feature got built. A subsequent reverse bounty seems to have raised nothing so far, perhaps in part because it does not appear to come with any guarantee (also the proposed feature is probably has a narrow audience and the reverse bounty is being called a “request for funding”–true, but very dull).
An assurance contract returns contributions (or cancels pledges) in case the amount requested is not raised. A dominant assurance contract returns contributions plus a failure payoff or refund bouns, making it worthwhile for interested parties to contribute even if they believe the contribution threshold will not be met. Both concepts could easily be applied to reverse bounties.