It sounds like what they are saying is that (a) NaturalMotion owns the copyright on the code, (b) NaturalMotion granted Justin permission to sub-license the code, and (c) Justin distributed the code under a BSD license.

However, the language defining step (b) ("granted by Justin Webb with the permission of NaturalMotion Limited") is hand-wavy and doesn't spell out exactly what rights are granted, so I would agree that this seems legally pretty shaky. What rights is NaturalMotion intending to reserve by including the following sentence? If there are any, do they conflict with the ability to redistribute under a BSD license? If there are none, why is that sentence there ar all?