Can I just plug the EthIR Beam into my own Ethernet hub without your EthIR Switch?
No. An EthIR Beam receives infrared frames from an infrared device and delivers these to the EthIR Switch. The EthIR Switch then translates these infrared frames to Ethernet frames (and vice-versa) forwarding and receiving frames to and from an Ethernet network. An Ethernet hub cannot translate infrared frames. That is the purpose of the EthIR Switch.