alt Hacker Newsas a generic aside, this seems like it's more of a "LAN of Things" project than an IoT device. It seems it would work fine if the upstream IP dialtone cut out for a while (though i'm guessing you wouldn't be doing too much video conferencing if that happened.)
but the core functionality doesn't require a server in the cloud, so by definition it's not IoT. just a nit though. it's still a cool little hack, no matter what you call it.
The definition of "IoT" requires neither Internet access nor cloud server functionality.
https://en.wikipedia.org/wiki/Internet_of_things
The core idea of IoT is that everything is capable of communicating on some network, whether that device is a fridge, a coffee maker, a dishwasher, a speck of dust, or a light bulb. The idea is that networks can connect more types of "things" than just general computing devices. The type of network and the reach of said network is sort of immaterial.
The author has created a specialized widget which communicates over a network. By definition, that is IoT.