I've hacked up an experimental arrangement to make most of the hierarchical libraries distributed with GHC work with Hugs too. The aim is to provide source-level compatibility with both GHC 5.04 and current Hugs. The main omission is modules related to the FFI, as well as various GHC-specific stuff. People accustomed to building Hugs from CVS may wish to try it out. See docs/libraries-notes.txt for more -- you'll need to get libraries and hslibs from CVS too.