Just extract the zip file somewhere, go into the extracted folder and launch the executable (RPG_RT.exe).
The folder also doubles as the source code; open the folder with RPG Maker 2003 to edit the game.
Markus Ranki ~ Production, design and game construction
Elisabet "Bulbiekins" Heikkilä ~ Background Art
Kasper "KVKH" Hjorth ~ Background Art
Janette "Juska" Kellokumpu ~ Character Art
Audio Assets from Presence of Music and On-Jin.