I believe it is part of Touchwiz. Someone may have pulled it from the stock rom for side loading. I don't have a link for it, but I am sure someone might. As much as I hate to ruffle feathers, you could check on the xda website as well. xdadevelopers dot com
The closest I have found to that and the HTC sense one are with HD widgets and beautiful widgets. They have many options but don't quite work like the original, but look just like them.
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