The switch would route frames as usual, and would only be concerned on the frames' destination and source MAC addresses, so the OS used in the network wouldn't be a concern, since the switch is only concerned with the computers' MAC addresses (granted that this is a basic, layer 2 switch).
One thing to keep in mind when mixing a Netware server with a Windows network is that the Windows client will need Client Service for Network service installed along with the IPX/SPX protocol to allow them to communicate with the Netware server. I think you can also setup a Windows server to be the gateway to the Netware server so that the clients won't need need additional software, since they'll just go through the Windows server for all communication to the Netware server.
