That's the issue.  You need Extended Fabric license on Brocade to ISL.  Thom
 Is it possible to connect a "Fujistu BX900 S1 - PY CB FC Switch 8Gb 18/8 14 (Brocade) running FOS 6.0.3b" into the same FC fabric as our two existing "EMC 6505 switch (brocade) running FOS 7.1.1" ?  I have tried to use the following procedure  and this resulted in the existing 6505 switch reporting status of segmented and zone conflict on the port connected to the Fujitsu switch. No merging of fabric or zone configuration happened.
Is it possible to connect a FC switch running FOS 6.0.3b to FOS 7.1.1 fabric?