|OSR blogosphere circa 1976|
I have absolutely no issue with his argument or his definition, but I do think it should be stated categorically that this is not a new phenomenon.
Even before there was an RPG hobby, the wargaming community was replete with hobbyists who thought nothing of taking an existing game and folding, spindling, and mutilating it. Witness the plethora of Diplomacy variants that flourished in the 1960's and 1970's, from versions that merely added Asia to the already existing map to versions (including one by Gary Gygax) who placed the game in Middle Earth.
Miniatures wargames were no stranger to this practice, either, and the early 'zines are similarly filled with alternate rules, new rules to add to existing games, and completely new games riffing off of previous work. Some of these amateur efforts were precursors to now-famous professionals within the hobby. But in addition, it was precisely this DIY ethic among the wargaming hobby that led directly to the creation of the RPG hobby itself. Witness Braunstein, Blackmoor, and of course Greyhawk.
Once Dungeons and Dragons was published, this DIY ethic didn't dissipate; indeed, it flourished with a new garden in which to grow. Thus we have Alarums & Excursions, Dungeoneer, White Dwarf, and of course Strategic Review (and later The Dragon), all adding to the still-flourishing 'zines. Thus, when Telecanter says:
"The OSR was more than a bunch of objects. It was a feeling of power. It was a license to create. It was a conversation. It was about examining our beliefs and revising them. It was messy and recursive. There was no end goal."mimeographs) of house rules from hand to hand, not to mention new spin-off publications like Chivalry and Sorcery and Arduin intended to "fix" D&D, that effectively were the Carcosas, Vornheims, Teratic Tomes, Labyrinth Lords, and Spellcraft & Swordsplays of their day.
While this DIY spirit never really died, it was severely tamped down by the rise of more professional productions, and the transition of TSR (especially, but not exclusively) from hobby publisher to professional publisher. There were surely variant rules, classes, etc. aplenty floating around in the 1980's, but nothing like the wild and woolly 1970's, and the Mayfair Games lawsuit in 1993 naturally had a chilling effect as well, leaving most players with "official" material, that which they wrote themselves, and little else.
I think what the OSR can most be credited with is a return to that DIY ethos. The availability of desktop publishing, print on demand, and blogs has served as the needed growth medium, and the OGL has been the restraining hand on the weed-whacker that previously cut down any dandelions that dared pop up, that has allowed such a flourishing of new creative material outside the control of "major publishers", and short of a severe new legal crackdown from WotC (which would be both dubious from a legal standpoint as well as self-defeating PR-wise, but is still conceivable), I don't see that ethos going away any time soon.