I gathered the vim part. Is he pressing a separate key to run the stuff in the lower-right window or is there a vim hook to do that automatically?
Left: vim with Vim Haskell Mode[1], a pale imitation of emacs haskell minor mode that nevertheless gets the job done. ;)
Top right: GHCi
Bottom right: Guard, as mentioned, using guard-shell[2] to compile the file and run main using runghci.
[1] https://github.com/lukerandall/haskellmode-vim [2] https://github.com/guard/guard-shell