House is an OS in a very different sense than Urbit - the "boots on bare metal" sense. The core of House is a monad which represents the hardware state of a common Intel box.
Urbit is intended to run virtually in the cloud and is an OS only in the sense of "stores your data and runs arbitrary programs". As a cloud computer its "function" is simply (old state, packet in) -> (new state, packets out). For communicating with the host OS this generalizes to "event in" and "actions out." Eg, I got an HTTP connection so I send an HTTP response. So not only isn't it done, it isn't even very smart... but it is a function and it is an OS.
Urbit is intended to run virtually in the cloud and is an OS only in the sense of "stores your data and runs arbitrary programs". As a cloud computer its "function" is simply (old state, packet in) -> (new state, packets out). For communicating with the host OS this generalizes to "event in" and "actions out." Eg, I got an HTTP connection so I send an HTTP response. So not only isn't it done, it isn't even very smart... but it is a function and it is an OS.