It isn't a gradient. For want of a better way to explain it, it is two copies of the same "logo", where one is darker than the second. The darker one is cut away and lain atop the first.
If you notice, the darker portion of the logo ascribes part of a circle. If you are familiar with Photoshop, using layers, and basic brushes, then follow this. If you were to create those three letters using the light gray, then select only those three letters, create a new layer, and then create a dark gray circle, copy only the portion you want, and paste it on another layer.
You would use pretty much the same technique.
EDIT Except you wouldn't screw up and leave a small amount of feather on the selection tool like I did :(