This is entirely an educated guess on my part. I would say you would NOT show the refund on the GFE. I think you would show it on your Cash to Close Summary or Details of Purchase on the 1003. I do hope everyone is working with a Cash to Close Summary so that consumers have a clear understanding of the anticipated bottom line. This is where you would show the seller assist, right?
On the HUD, I'd probably put the FHA MIP refund on page one where the other credits go.
So that's my take without popping up onto the FAQs since I presume you already checked them and the issue isn't specifically addressed there. ;)