Serenity Role Playing Game is a science fiction role-playing game released in 2005 and set in the universe of the movie Serenity. It was produced by Margaret Weis Productions, Ltd, and its mechanics were the first iteration of the Cortex System. It won an Origins Award for best RPG in 2005 and Margaret Weis' license came to an end on January 31, 2011.
In February 2013, Margaret Weis Productions announced they now had a license to produce a game based on the Firefly TV series, this time with the rights to the characters who appeared in the series rather than those who appeared in the film.
Source: Wikipedia, "Serenity Role Playing Game", available under the CC-BY-SA License.