”    Normally I don’t encourage much ad-libbing, but with Heath, I just let him run.” Parnassus still has not landed a domestic distribution deal, fostering speculation that it may be too unusual to find a wide audience. (It does have an international distributor and is set to open in the U.K. in June.) One source close to Gilliam speculates that the director — an American expatriate who has often found a welcoming audience for his work in Europe — may be hoping that a buzz-filled Cannes debut will lead to a distribution deal and a domestic release in the fall.