`python.rb` seems to contain some code very specific to python itself. This is not the case with `cabal-install` which is like `pip` for haskell. Also `cabal-install` is used in an unusual way in order to keep only a executables and discard the libs in a formula — again this is not much related to haskell.

But I actually don't know homebrew well enough to make a decision — I hope you'll get more useful comments from the others :-)