Maybe I'm just late to the game and everyone here's known about this for a while. I searched the forum and found no mention of Movie Battles. So I thought I'd post my experiences so far.
I downloaded Build 17 and installed it. There's no installer for Mac, just a .zip file with the files and folders and a readme explaining where to put stuff. At first I couldn't figure out how to run the mod, but found out that you launch it from the menus of Jedi Academy Multi Player.
There was an earlier version of
Movie Battles for Jedi Knight II: Jed Outcast. The current versions are for Jedi Academy. The maps are spacious and sumptious. Character models are detailed, new animations are cool. I loaded a solo game to try out the new saber moves. They take some getting used to. Then I joined a game in progress.
All the normal multiplayer games are playable, but if you search of
Movie Battles games online, there are a fair number of active servers with plenty of action. The
Movie Battles are task based, for instance, trying to load frozen Han onto Boba Fett's ship if you side with the Imperials, or trying to save Han if you side with the Rebels. Tasks usually take 5 minutes to complete. Points are tallied up for kills, objectives met, and those left alive. There are limited character class types available ('cause there were already enough Jedi and Mandalorians, so I went in as a stormtrooper and had a blast getting killed! You can play as a Storm Trooper, Clone Trooper, Jedi (Luke, Annekin, Obi Wan (Padawan, Knight, Old Ben), Sith (Darth Maul, Darth Vader, Darth Tyrannus, dark Jedi, Reborn, etc), Imperial Officer, Madalorian, Rebel troop, really almost any character from the games or movies as long as the server allows it. It's totally different from JA. Like a whole new game. For free.
Build 18 is due sometime this summer! Best online gaming I've done, and I'm only beginning.