...Traveller did start as a campaign-less system, but to your point RAW with specific Tech tropes. A campaign universe has evolved as a logical extension of that ruleset. But like Mike, I did homebrews with other tech assumptions and tropes (my nickname ^^^ comes from my WellWorld homebrew) and even a TL7 spy game with the "gadgets" being TL8 and 9 devices. In the last in the last 10 years "Traveller" has evolved beyond that origin. We even have magic now (thanks Samardan Press!).
This discussion with aramis got me thinking in a reverse sort of way. Over the years, I have done many conversions. Many of us have done them. But....The tech tropes and jump drive are the same in every edition. the details vary a bit, but the tropes generally remain.
The Jump Drive is near-unique - the few authors whose universes have a similarly constrained FTL mode are connected with Traveller - most notably MJD, Jeff Swycaffer, and Chuck Gannon.
And, to be blunt, if you use the jump drive as written, it provides a large part of the feel.
Why did you use a different rule system and convert the OTU into it?
What was Traveller as a set of rules lacking that the other game had or what was the zeitgeist in your group?
Like right now I am doing the OTU in Vortex System (Doctor Who). My reason is I want to represent the OTU in a simple tabletop system for pre-teens where characters don't die quickly to get/keep them interested in RPGs. Vortex has Story Points (get out of death or change the story a little). There are only 12 skills in Vortex. Dice mechanics very similar to MgT1e/Cepheus.
and, I like mashups. Who doesn't want to see Imperial Marines vs. Sontarrans or Daleks?
What say you?