When installing the MDK file icon appears with which you can modify the system of the game separately, for example think of a storyline, quests, change the texture and so on. The player will be available in almost all the material the game, but the editor will be limited (at your discretion), and of course there will be some copyright.
About the movie, it can be done as a separate option, a button in the editor and interface changes to create a machinima, which will be stored as on Fraps after being edited in Vegas and then the players will be doing voiceovers, approximately
. The interface will be given a certain call options NPC, its animation, the point where it will run, gestures and so on. also establish multiple camera switching and more comfortable shooting, change the settings for the camera, well, then you yourselves know better!
Thank you very much for your answer!