I don't have a video game, but I have posted a board game, free to all fans. The link is below. I am currently finishing up a card game called BWAH! which I will also try to get into the hands of fans.

TCM

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Recreate a bar fight or even the Battle for Serenity Valley in

Firefly: BIG DAMN HEROES

my newest creation! A customizable strategy boardgame based
off the very show we all love! Download it at
http://homepage.mac.com/gojiro42/PhotoAlbum10.html
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Well I'm working as a Graphics Artist and 3D Modeler for the "Escape Velocity Nova" Firefly Mod. Its a free fan made mod (well you need to own the game we are modding).

This is our Forum so if anyone has some skills and would like to help or if you want to see some of our work stop by:
http://s4.invisionfree.com/GunRunner/index.php

Well there are a few publishers that will help make games that have a dedicated following like Battlefront.com. I don't know of any for Sci-Fi...

I'd be very surprised if one turned up for Serenity (apart from the fact that it would have been announced by now). Games cost lots of money nowadays and publishers will only use a licence if it practically guarantees huge amounts of money (e.g. Harry Potter, Star Wars, NFL, etc)

Maybe by the time of the sequel though.