That first link you gave is FILLED with A LOT of horribly outdated information.  If you read that entire article, it would be extremely clear that is not a reliable source.

The second two links are also horribly untrustworthy.  They both use the same 'source', they call it the "Metal Roof Tax Credit" (it has NEVER been called that) and all of the links point to that FIRST link that you gave (which as I said before, has obviously grossly outdated information).