Is the keyboard on the 15" Mac Book Pro with Retina display different than others in size? I just got a new 15" Retina MacBook Pro (rMBP) for a friend and looking for a good keyboard guard/ cover. I know shopping questions are off topic, but I'm wondering if the sizing is something that differers between Mac models.

I have Moshi ClearGuard for my 2009 15" MBP. Would that work for the rMBP or do I need to look for something specific to Retina models?
No need to worry - at present, the only MacBook with a physically different keyboard size (in the US) than the rest is the 11 inch Air.

The small Air has a full sized "main keyboard" but the top row of function keys are slightly smaller than the top row of function keys on the rest of the lineup. I would presume that the same holds for international key layouts when they have different enter keys or additional physical keys, but don't know that fact for sure.

The cover you mentioned will fit the new retina MacBooks - both 13" and 15" - as long as the hardware is a US model.