ARSE is short for ANH:R:SE which stands for "A New Hope : Revisited : Special Edition" which refers to the HD redo of "A New Hope : Revisited" that Adywan'll be doing after he does ROTJ:R but before he tackles his prequel project.
It has associations in my head with the line that someone on here came up with about how Lucas's attempts at fixing the films are only half-assed, but here at OT.com, we go full-assed!
But yeah, it's a joke.