The Zoo lets you share Rhino, Flamingo, Penguin, Brazil, and Bongo licenses (CD-Keys) among users on the same network workgroup. When these products are installed as the workgroup nodes instead of stand-alone, it works like this:
The Zoo is free!
Download Zoo 5 for Rhino 5 and Bongo 2.0 (Rhino 4, Flamingo, Penguin, Brazil, and Bongo 1.0 not supported).
Download Zoo 4.0 for Rhino 4, Flamingo, Penguin, Brazil, and Bongo 1.0 (Rhino 5 and Bongo 2.0 not supported).
Note: it is possible to have both Zoo 4.0 and Zoo 5 running on the same network, and even installed on the same server, without conflict.