You can do the script (which I’ve never read) and let it inspire your decisions. But how can you be free from the film version? How could you be free from the film if you decided to do The Sound of Music?
RHPS is an interesting case since the fans tend to know every frame of the movie. And part of being a fan is being able to stage perfect lip-syncable facsimiles which run in tandem with the screen action. Any fan, therefore, could direct a great production if reproducing the film is the goal. And as a goal, why not?