I don't know if I can do much more for Risus: Firefly that hasn't already been done by Anjin.

Wikipedia is a good source for reference if you do not own, or have not seen, the series.

Background
Firefly was a short lived Sci-fi show on FOX that detailed the trying times of a ship named Serenity and its' crew set some five-hundred years in the future after humanity took to the stars and began terraform planets. It was their (the crew) goal to continue to be 'independent' after the loss of the 'War of Independence' by taking to the sky.

On Culture - the colonization and terraforming of the planets was predominantly done by the two largest remaining powers of 'Earth-that-was'; the U.S. and China. Much of the culture of the Firefly setting is stapled by the merging of these two powerhouse's culture; from their dress, decor and speech. The firefly setting has a strong semblance to the 'Wild West' of history's past.

On The War - the 'War of Independence' was fought between the Alliance and the side for Independence - the "Brown Coats". The war was over with the loss of the battle for 'Serenity Valley' by the Brown Coats. Even though the Alliance won the war, their control is mostly limited to the two main Alliance Planets. The farther one goes into 'The Black' (or away from these Alliance held worlds) the more Independence is seen, but at a cost. This Independence is at the cost of not being supported by the Alliance with medicine, food, and protection.

On Tech - though space travel is common, technology is rudimentary at best. Weapons are similar to 21st century slug-throwers - though the ammo and ammo capacity have been improved through case-less ammo. Though lasers are present, they are usually only seen within the Alliance and are VERY rare. It is speculated that a long ago passed gun control legislation, by the Alliance, limits the availability of any 'newer' styled firearms.

On Humanity and Reavers - lawlessness increases, as well, as one travels into The Black. But nothing compares to the lack of the humanity of the 'Reavers'. Reavers are believed to be humans that are driven mad by living on the edge of space while their very existence is denied by the Alliance. Reavers are known to kill, rape, skin and eat anyone they run across and not necessarily in that order. Zoe is quoted in the series by saying, "If they (Reavers) take the ship, they'll rape us to death, eat our flesh, and sew our skins into their clothing. And if we're very, very lucky, they'll do it in that order." Reavers run their ships hot, known as 'running hot', which is without proper radiation shielding. This makes their ships much faster but easier to detect. Typically Reaver ships look battered, from their use of them to damage other ships, and are usually adorned with red stripes and bodies of the people they have mutilated.

Playing Risus: Firefly
Optional Rules Used
Character Creation
Ships
Slang
Examples of Play
Adventure Ideas