Classic Traveller:
Marc Miller produced the trilogy of Traveller. Three small black books, or
one big one, depending on when in the 70's or 80's you bought it. The rules were
simple, the action fast. The Imperium was big and intact. The Zhodani were
the bad guys, the Vargr were chaotic, and computers were big.
Of course it wasn't that really that simple. Serious Traveller players used
Book 4, Book 5, and Book 6, at least. They also used
JTAS articles, and the nifty stuff from Paranoia Press.
Now being republished in Big Floppy Book
format.
MegaTraveller:
In the mid 80's came a new version of Traveller. Several 8.5x11" books with
brightly colored covers. The rules were deemed good, once you had all the
errata. The design rules were complex, but allowed construction of fusion
powered roller skates to star ships. That is, once you knew were the bugs
were.
MT also brought the death of the Emperor and the start of the Rebellion.
Many embraced the change. Others clung to the days of a stable Imperium.
Some fled the Errata beast of MT. Many fled their Traveller, others invoked
the rules of GURPS to maintain their Campains.
Traveller:The New Era:
Traveller under GDW's House Rules. Major changes to mechanics and the setting.
The Imperium collapsed (but a Flame still burns in the Spinward Marches)
under the weight of the Rebellion and the VIRUS. Many use the new
rules, but a CT setting. This disappeared when GDW went
out of business.
Traveller, Mod IV
With
GDW ceasing to do business, Traveller rights rights have reverted back to the orginal author, Marc Miller. T4 (as in the 4th rev of Traveller) is out. It's based on the CT rules. It's also know as Marc Miller's Traveller. The big change is the setting. The time is Year 0 of the Third Imperium.
This was published by Imperium Games.
Imperium Games dropped it's support of the Traveller line due to bad investments overseas.
Marc Miller pulled their license to publish Traveller material, in part due to books that made MegaTraveller look errata free.