True, traveller now has multiple settings and multiple rules systems which is a bit confusing / bit of a pain. But this is more of a IP issue rather than problems with any specific traveller publisher. Its really up to the owner of the IP rights (and a delegated line editior) to keep the flavour of traveller consistent and stop publishers wandering of on a tangent.
Is it really worst than say D&D (basic / expert etc. + AD&D (4 versions now) + multiple settings (greyhawk, forgotten realms, dragonlance, misc generic + some new ones)
Cheers
Richard
D&D 3.x/4.x isn't in the AD&D tree... mechanically, it's closer to the Metzner tree. (Yes, really. I've run all the below, and while S&P has a skill system, the rest of the system is more congruent to the metzner and revisions of the metzner tree... despite greyhawk... and my older copies of Greyhawk include notes for the metzner ed as well as the Gygax AD&D...)
Tree 1
1st Ed D&D: Little (Brown or White) Books (Gygax/Arnesson)
2nd Ed D&D: Metzner Basic (Blue)
2.1 D&D: Metzner Red Basic & Blue Expert
2.2 D&D: Revised Basic and Expert, plus new Companion, Master, and Immortal sets
2.2.1 Basic/Expert/Companion/Master plus Gaz and HollowWorld rules expansions
2.3 D&D: Cyclopedia and Wrath of the Immortals
2.3.1: 2.3 + Gaz & HW & Race Expansions
3.0 D&D: WOTC D&D 3E
3.5 D&D: Hasbro D&D 3.5E
4.0 D&D: Hasbro D&D 4.0
Tree 2
1st Ed D&D (G/A)
1st Ed AD&D (Gygax)
1.1E AD&D (Gygax) 1st Ed + UA, FRA, DLA, GHA
1.2E AD&D 1E + UA + DSG/WSG
2.0 AD&D: 2E core
2.1 AD&D 2E Core + Complete Guides
2.2 AD&D: 2E + Player's Option/Campaign Option series...
(tree may be influencing other tree...)
3.X AD&D: Hackmaster