[AdrianEGraphene]

Yes, I took great inspiration from HashCash and Proof of Work in general.

Re: minus the refundability

The refundability is the main thing that allowed us to patent this. HashCash, and the large PoW required by Bitcoin are meant to strain any attempt to transact on the respective network. Ours only strains bad callers (monetarily) and does not strain good callers.

The argument we presented was that good/bad callers can be simplified as calls that lasts more/less than some time threshold.

Simple, user-friendly, intuitive, and serves the purpose of disincentivizing high volume spam calls while giving legit unknown callers a chance to bypass the blind filter.