Over there on a RPGSite forum thread, the question was asked: "Why don't the Traveller people do OSR?" (OSR stands for Old-School Renaissance, i.e. the retro-clone and retro-module movement for D&D-type games). So, indeed, why didn't we see such a movement develop for our beloved Traveller? There are several reasons for this.
First, You can buy a CD-ROM with all the Classic Traveller stuff (very many books/adventures/aliens/games) in PDF for $35 from Far-Future Enterprises (FFE). Another $35 and you get all the JTAS magazines. You can also buy The Traveller Book in Print-on-Demand on DTRPG for $20 + Shipping. So all the OOP stuff is easily and cheaply available... For Dungeons and Dragons, for a long time, PDFs of most 2E or earlier products were not legally available, and reprints were typically expensive, spurring the rise of the OSR, as players and DMs interested in earlier versions wanted something affordable to play with, so they devised retro-clones.
Second, FFE has a very liberal fair-use policy. You can essentially write anything you want for Classic Traveller, and openly claim compatibility with Classic Traveller, as long as it is provided for free. So you can easily publish online and for free anything you want for Classic Traveller (or any legacy edition of Traveller for that matter, with the possible exception of GURPS Traveller) - no need for an OGL-based retro-clone to base your writing on.
Third, Mongoose Traveller is essentially a retro-clone - an official, supported, in-print retro-clone of commercial quality available for players who prefer a more modern layout than that of the old books on the CDs. So if there is an officially-supported "clone", why write your own?
Fourth, Mongoose Traveller has an OGL and an SRD and even a compatibility license; all allow for commercial publication. A good number of commercial third-party products are now available for Mongoose Traveller, which are perfectly usable with CT (I wrote one - a whole setting, Outer Veil). Also a good number of Traveller fan-made settings and blogs around. In essence, you can publish almost anything you want, commercially, for Mongoose Traveller and openly claim compatibility provided that you don't touch the official setting outside of Foreven. And MGT is close enough to CT so that your products will be quite compatible with it as well.
Fifth, there was much less of a break in continuity in Traveller than in D&D. Nowadays, most Traveller players, which the exception of those who play GURPS games, seem to play either Classic Traveller or Mongoose Traveller. Many of the in-between editions, such as MegaTraveller, Traveller: New Era, Marc Miller's Traveller and Traveller D20 (AKA T20), seem to see much less actual play. This is quite different from the D&D situation, in which many players moved on to play 3.xE and 4E, and, before the OSR, relatively few played Classic D&D.
So there is significantly less actual need for an "OSR" for Traveller compared to, say Dungeons and Dragons.