Birthright is a Traveller game focussed around the crew and passengers of a small trading vessel, working to make a living in a sector of space that lies at the end of a long trade route to Earth. Day to day, the job consists of taking whatever passengers or freight haulage jobs are going and in buying up goods to sell at other markets. The nature of tramp trading being what it is, the party are likely to get into scrapes, take odd jobs to supplement income and fall foul of changing conditions and events. They’re not adventurers, just merchants who have adventures. However, during their travels, the crew may meet characters whose lives have been more action packed, or get involved in schemes with a lot of backstory. In this case, the players will get to experience a little slice different parts of the universe.
While not the Official Traveller Universe, the setting does owe a lot to it. Interstellar travel consists of week long jumps, during which a ship is totally cut off from the rest of the universe. A feudal structure keeps the worlds of humanity tied to a single monarch. Science, while advancing in understanding and applications, has not fundamentally changed human interactions or the way they perceive the universe. However, unlike the OTU, there are no ‘intelligent’ alien races, nor are there major external human civilisations to conflict with. Technology has not reached the same levels, particularly in the field of gravitics. Jump drives are limited by legal restrictions rather than by increasing technology. And there are absolutely no psionics.
Other major influences are Starship Troopers (both on planetary warfare and in different political systems), Battlestar Galactica (on space combat and for doing gritty space opera well) and 2300AD (for injecting a very small amount of much needed hard sci-fi). Plus I’ve shamelessly pilfered spaceships and vehicles from other settings. Expect Vipers, Star Destroyers, Colonial Marine dropships etc.