Ask Keith whether he'll let you use it.
Thats a nice Invision styled borad
jah he verry good !
I want thats theme :s
If you really want this theme, all you can really do is what Phalanx suggested, and ask Keith whether or not he would be willing to release it.
If he is prepared to release his theme, then you can use it, but if not I'm afraid we can't help you.