The core interface of wxHaskell was originally derived from the wxEiffel binding. Work on this has been dormant for several years, but the wxHaskell maintainers now support updates to the wxWidgets API themselves - we generally respond to new releases of wxWidgets within a few weeks at most.
Regardless, this is an exciting development. Once it's reasonably stable I will migrate my hobby project (http://spek.cc) to use it!