Yes, started in 1978 right after I got the three LBB, didn't even know there was an OTU for some time.
So no variant or re-working, designed from scratch and not very Star Wars or Asimov Foundation like as the OTU.
Inspiration for the setting came from my favorite Sci-Fi authors of the time: mostly Frank Herbert (Dune and Dosadi series), Larry Niven & Jerry Pournelle (Known Space and Co-Dominion series), Robert Silverberg (many except Lord Valentines Castle), Robert Asprin (The Bug Wars), Robert Heinlein (Starship Troopers), Harry Harrison (The Death World Trilogy mostly) and James White (Sector General series). Healthy doses of inspiration also later from Cherryh (Chanur series) and David Brin (Uplift series, although the idea of "uplift" I'd included earlier through inspiration from the story "A Boy and His Dog").
Enough of the muse, the setting is about 3,000-3,500 AD or so, never fixed it exactly, which I call the Lost Colonies campaign. The campaign is centered around a region of space (a little past Bellatrix) settled by a human STL colony ship about 400-500 years ago. The humans have succeeded admirably and have expanded from their original colony to inhabit about two dozen worlds.
The main world after a couple of hundred years went through a "revolution" and a new STL colony spun off a couple of parsecs away (think LeGuin's "The Dispossesed"). Both colonies grew. The younger colony discovered jump drive and the humans went through a micro-expansion until they started to come into contact with aliens.
A little about why the humans are here. The STL colony ships left Earth when it looked like they were going to lose the war with the first alien species they met. The best image I can conjure is imagine what the humnas in the Man-Kzin wars thought when slowly the Kzin gobbled up the human colonies and then a massive fleet (all STL then) was detected heading to Earth. People paniced and a slew of STL colony ships were sent out, The First Great Exudos. No records were made of were they we're going, for fear the Kzin-like aliens would follow. Hence "The Lost Colonies."
Now back to the campaign center. Stars within a region heavy with nebula were chosen for the colony to avoid detection and to provide some cover as IMTU, nebula make STL travel more dangerous (and FTL travel as well). So the human's were hidden in their little nebula pocket, as it were, for some time from the local aliens. Now when the humans encounter these local aliens there was a bit of tension as humans were a bit paranoid of aliens, veiwing them as genocidal at best. Luckily the first aliens they met were friendly traders who introduced them to the local political neighborhood. The Lost Colonies are in an area of several small alien polities (2-5 systems each) and two "massive" polities 24+ systems each. All of a sudden the humans are a new player on the block, although they are divided and war amongst themselves, and are not the most technologically advanced. Due to the nebula there remains regions of space unexplored that a fairly close by for those crazy enough to brave the navigational hazards.
IMTU there is also an Imperium, but not like the OTU one. No Vilani, no ancients etc. It is just off the edge of the campaign focus and the plan is to have it come in contact with the lost colonies.
Overall big picture, IMTU I explain the Fermi Paradox as follows. Roughly 3 billion years ago the first intelligent species arose in the galaxy, The Seeders. They looked around via STL (they never discovered FTL) and found they were alone. Depressing for them; so two factions took two different roads. One sent out seeder ships, STL self sustaining robotic controlled ships that were sent out to prepare worlds and seed them with life that hopefully would evolve into something like The Seeders. (Hence the reason there is a larger fraction of oxygen/ nitrogen bipedal life than by pure chance and why "food" from one world can often grow on another). Another faction of The Seeders decided to create intelligent species (think for example, The Progenitors in Brins' "Uplift Series"). That's another story.
Now this Seeder activity is the source of many woes for the region of the galaxy humans find themelves in. Over hundreds of millions of years many of these robotic seeder ships became aware, sapient. A portion looked back on what they had done and felt guilt, as in preparing worlds the often sterilized the surface first. They have come to view The Seeders and their progeny as "bad life." Some wait in space until they hear radio signals from a world, then proceed to clear it of "bad life," usually by bombardment with cometary fragments as they don't want to steralize a world just clean off the "bad life." Others merely contain the "bad life" in system. Still others periodically roam and destroy any bad life they find (one reason why mass extinctions on some worlds follow a very cyclic pattern). Still others focus on protecting independtly evolved life. Still others yet don't believe further destruction is the answer, and try to shield systems by "stopping/blocking/scrambling" radio emissions from the system. The zealous seeder ships make the galaxy a very dangerous place. But they are all STL with drives that a very hard to detect so they go unoticed largely as they crawl, almost leterally, between the stars. Luckily, not all regions of space are covered by these ships and they are the target of another species.
The other major threat are called simply The Bugs. They are actually several different species who have joined together. There actions appear random to humans (as they are typically emergent intelligences with a matrix -like thought process) but what is know is that they tend to travel to a system, settle it, clearing worlds of all higher life and farming them. After a while they leave (hence in some regions of space "garden worlds" with much flora and some fauna but with little variety or higer life are found) and move on. Great swarms are rumored to sweep the stars at STL and some at FTL. The Bugs and most Seeder Ships are mortal enemies. So IMTU, it's a dangerous place with seeder ships and bug fleets lurking between the stars and explaining the Fermi Paradox.
MTU is also a place of many aliens, the progeny of The Seeders. A fair number are bipedalish but a large number are not. The non-Seeder species are rarer. The Imperium is dominated by human systems but there are many alien polities that weild great power in the Imperium. The Imperium is more a military and economic association of many power blocks. The Imperial House is usually the most individually powerful group of worlds that have formed the most powerful power block. No one power block is strong enough to ignore all others and rule by fiat. Currently, IMTU the Imperial House is a human one (which is typical) after coming out of rule by a very corrupt human house (Think "Dune" and House Corrino and House Harkonnen).
This is just a quick overview since I skipped over the second wave of spaients that arose (all non-seeder life) and the Curators who came later and tried to carry on The Seeder work as they saw it.
I can go over the local conflicts/politicas in the Lost Colonies around Bellatrix, and/or those of the Imperium or the other non-imperium forces out there if you'd like more.