The peanut butter is the dominant flavouring component of the stew; everything else is a modifier of it, really. Yes, other things could be substituted, but it would be a very different dish.

Possible alternates: roasted-chickpea butter (sold as a peanut-butter alternate; I haven't tried it); other nut butters. Going farther afield, many grocery stores sell pouches/packets/jars of curry paste, and I've used them to make similar chick-pea dishes in my crock pot.