I say that because fedora-haskell gives the release date of 6.4-7 as 11-May-2005 while the release date of 6.4.1 is 19-Sep-2005.
The fedora-haskell project is for Haskell-releated RPMs that are not yet included in the more official Fedora repositories. GHC recently made the move into the Fedora Extras repo, and there you will find an up-to-date GHC 6.4.1. A simple "yum update ghc" ought to bring the earlier poster up to date.
The older version of GHC, however, remains in the fedora-haskell repo for historical purposes.