preface: Wow... out 2 days for real life and getting into grad school, and the argument explodes. I'm addressing stuff as far back as page 4.
AD&D 2 and Feats: more properly, kit special abilities, and many of the weapon proficiencies in the Player's Option system are in fact precursors to the 3E feats.
Alternity and Feats: Special abilities purchased by some when requisite skill levels are had.
Task Systems:WEG-SW, 1987, had a task system. T2300, 1986, had a variant of the DGP-CT/MT task system. LUG-Trek & LUG-Dune, D-Trek, and D-LOTR are also Task based. RM/SM are right on the border between skill systems and task systems in the editions I have (pre 1995). Every WWG game has a task system. Lots of systems have coherent difficulty systems for their unified skill mechanic, and are arguably also task systems.
T20 and GT: They are not valid versions of traveller for the same reason that 3E isn't AD&D3: lack of mechanical similarities. Likewise, the complaints by Dragonlance Fans of the AD&D variety about DL5thAge... no mechanical relationship to AD&D, and thus invalidating all their characters, as well as destroying the setting. (Truth is W&H did that in the novels, and TSR used it as an excuse to launch a rather good game to a popular setting and not have to port all the D&D spells... but it failed for a number or reasons. It wasn't D&D, and so it didn't feel like DL to RPG fans, and the non RPG fan DL5A gamers were few)
GURPS works for some, but it has very non-traveller ways of doing a lot of things. the OTU setting could be properly ported to a GTU universe; the extant GT is neither very GURPS nor very Traveller-Mechanic, and is arguably not even terribly faithful to the Traveller-OTU. Characters are not inter-useable, nor easily convertible.
T20 is likewise not mechanically similar; a lot more effort was put in initially (and thus far less needed later) to remain as mechanically Traveller as D20 players could handle. Characters are incompatible.
TNE is only marginally character compatible, but uses a similar task system, the same atts (just add 1 to each), and roughly twice the skill levels as CT/MT.
MT is much more compatible; craft from one can be easily used in the other, albeit with a little effort. Characters are directly compatible, albeit with about 15% more skill levels, and thus hitting the Int+Edu limit.
One could see the mechanical and setting growth.
Even T4 shows clear mechanical relationships with TNE and CT.
Heck, 2300 is more compatible than GT, and about on par with T20, in terms of mechanics. And t2300/2300AD is NOT usually considered a traveller edition.
Also, few companies count ports to other systems as "Versions" for their version numbers. BTRC doesn't count the port of CORPS first ed setting to Active Exploits as a version number for CORPS.
Based upon Mal's argument, HeroTraveller needs to be counted, too...
T20 and D20
During the playtest, Hunter discussed with the playtesters the ideas of going to a less-level-based approach. Also discussed were 1 term=1 level, attribute based damage ala CT, realistic trade system versus fun trade system, etc. For better or worse, DrSkull, J-man, Myself, and a half dozen others made decisions based upon targeting D20 players. Even whether or not to go D20 vs OGL was discussed. Flat out, don't blame hunter for those decisions; we, the playtesters, guided his hand and like a good game designer should, Hunter Listened!
We were given three goals:
1) to attract D20 players to the Traveller game line.
2) to not alienate the grognards with the system
3) to keep it close enough to use CT non-character stuff.
On point 1: That killed term=level. THat also killed level-less, as no successful systems at the time (IE, none that any of us had seen commercially released) had done level-less OGL/D20.
On point 2: many of us were grogs... so we picked and kept what we could keep whole cloth, adapted some, "updated" a few to meet common fan-requests, and developed some of the D20 methodology away from stock to provide travelleresqe results.
Yes, you can drop HG ships into T20, and vice versa. The results will be similar, not identical. Yes, we exploded Bk1. It may be less realistic, but it is simple, fun, and playable, and allows one to, with a well developed crew, make a consistent profit by trade or spec, and if not by spec, then by the skin of the teeth. It feels right to me, and it works for play.
On point three: we wound up turning that one on its ear; large chunks of T20 are specifically designed so that a one page conversion guide (almost superfluous) would provide the conversion factors to use it in any other Mechanically-traveller ruleset.
Mechanics vs Setting By the time Traveller got competition worthy of the label, the OTU and the Rules were being seen as interrelated and nearly inseparable. By 1984, the setting was being hashed out, and expanded, not just in Traveller, but also in Striker, the Traveller board games, JTAS, adventures, supplements, and in fanzines.
Taking one without the other isn't fully traveller; likewise one could run a non-StarWars universe with the D20 SW rules, or Torg using Traveller, or Traveller using Torg/Shatterzone/masterbook, or whatever. the OTU has been adapted into at least a half dozen rulesets by various gamers, even before GT was announced: CORPS, GURPS (preGT), Interlock (CP2020/Mekton), 2300, AD&D, Hero, FUDGE, Masterbook, WWG's StoryTeller, Space Opera, and BRP.
The setting has always been separable from the rules since the 1975 release of Tunnels and Trolls; it doesn't mean that it should be separated. Of course, D&D developed into several official settings and innumerable unofficial ones; T&T still has one much looser official one. Traveller has had one, arguably two (PreAtlas and PostAtlas) settings as "official" and scads of unofficial ones, and as the setting became detailed enough, it was adapted to whatever fancy suited the GM.
But NONE of that invalidates the need to have some form of official setting assumptions, even if not a full blown setting. Traveller is best defined by these assumptions: Jump Drive, no FTL-comms, excessive habitable worlds, artificial gravity, and adventurers who are basically different from Joe Normal only in deciding not to retire, but to seek fame and fortune amongst the stars. Those elements are enshrined in the CT, MT, TNE, and T4 rules. One of these is actually directly counter to GURPS: that adventurers differ ONLY in motivation; GURPS implicitly states that normals are 25 point characters (3rd ed revised).
2300 is not considered a traveller setting because it DOESN'T adhere to those same assumptions. Instead, they have Sttutterwarp, no AG save spin, no FTL, and again, adventurers differ mostly in motivation.
This is counter to it's competition: Space Opera gives PC's explicit bonuses for being PC's. GURPS is built upon the assumption that normals are in fact less capable than PC's and significant NPC's. AD&D says normals are Level-0, and PC's start better; it does have a lot more implied "PC-type" characters.
I can see Traveller without the OTU, but I can't see OTU without the enshrined assumptions about PC's; the other assumptions had to be patched somewhat for Traveller Ports.
