Nick W. requested I post this here, so here's the abridged version. The full thing is up on my blog if you haven't yet caught it.
PART 1: Dandy's Eightfold Path
OSR games are...
Original -The game content setting and rules are novel and/or shares lineage with variants of the OD&D ruleset. It is not required that both of these be active simultaneously.
Simple - The core rules are easy to explain and learn. They can be understood easily by new players, children, drunkards, and the occasional very clever dog.
Ready to Hack - The game is modular, so it is trivial to change rules, add mechanics, make substitutions, and otherwise incredibly easy to make your own material.
The act of play is...
Organic - The story and world are emergent, coming into being during the act of play. Random tables, player input, whim + foppery, and chains of consequences all play into this.
Skill-Based - A player's skill at navigating problems with novel solutions is worth more than the character's mechanical skills. Unorthodoxy is rewarded.
Reactive - The world of the game is not static, nor does it conform to a set of genre expectations. It exists outside of the players and reacts to their actions. Consequences are enforced.
And finally, the most important...
Make Cool Shit - You know that cool shit you want to exist but doesn't? Make it. Make it yours. Make it the coolest shit you can make. Life is too short to wait to let other people make shit you think is cool.
Fuck the Man - The Man is not your real dad and therefore cannot tell you what to do. Your own real dad can only offer polite suggestions on what you should do, if he is a cool dude. Submit to no authority. Silence brands. Publicly humiliate Nazis. Murder the gods and topple their thrones.
There are schools of the OSR as there are schools of wizardry or schools of philosophy or schools of sci-fi. There can be no "true OSR", because purity is a lie unbefitting an entropic universe. All of these are malleable, shifting, overlapping, intermingling, and otherwise inconstant. A single person can and will be a member of multiple schools at a time and can shift between them according to both time and specific projects. There are certainly schools I have left out. They are all subjective, except for the Regressive Wanker School.
Retroclone School - Focused upon games that revise and repackage OD&D, B/X, etc, without major additions or modifications. Labyrinth Lord, OSRIC, Lamentations of the Flame Princess.
Regressive Wanker School - Those who spend far more of their time complaining about SJWs and/or storygames and being unpleasant to be around than creating cool shit. Love playing victim and proclaiming over-inflated self-importance. Pundit, Venger, Zak. Goblin School -The very particular flavor of weird originating with Arnold K. Includes anyone who plays around with the GLOG and I lump most bloggers with their own bespoke weird-takes-on-vanilla-fantasy settings here.
DREAM School - Hybrid school experimenting with storygame elements. Lightweight, personal, Itch.io and Twitter based. More of an inclusive social contract than a specific set of dev guidelines, but many DREAM games share the similar traits listed.
Dog Knight School - Grotty, cynical, gross, decadent, obscene. Eat trash do crimes. Fuck the Man. If Fiona Geist likes it, it's probably Dog Knight.
Light and Cozy School - Light and comfy games with a lot of influences from fairytales, cartoons, and JRPGs. BREAK! is the poster child. Counterbalance to Dog Knight.
New School Old School - OSR attitudes towards play but sprouting off into complete new rulesets and genres. Mothership, Maze Rats & Knave, Esoteric Enterprises, TROIKA!.
Hardcore Artcore School - People who get really artsy and out there. Patrick Stuart and Scrap Princess.
Orbital School - People who don't identify with OSR as a label but the games they make and their styles of play fit right in.
Fiver School - Folks who do mostly 5e (or close to it) stuff, but they still have the energy to them. Jack Shear and Kiel Chenier.
The Generally Cool School - Individuals who are off doing their own thing and killing it. FLAILSNAIL School - The "who cares do whatever" school of gonzo, as spearheaded by Jeff Rients. Anything goes, everything is cross-compatible.
The Big Time School - Games that have broken out into the big leagues (or what we have of them). DCC and Shadow of the Demon Lord.
Alignments are for Suckers School - For those who neither have nor want a school. Rock on, people.
Since the original posting this has taken off and people seem to be pretty fond of it. I don't know how helpful it will be in the long run, but it should be a decent reference for folks in the future.