A floating workstation license supports the use of Iray for Maya up to a maximum number of users or “seats”, who are connected to a server network. The products can be installed on as many computers as desired; however, at any one time, can only run on the maximum number of computers for which licenses have been purchased.  Because you can install the products on more systems than the number of licenses purchased, you get true floating licenses across your entire network.

By default a software licensing is supposed to be used by Iray for Maya.