Great thread. Like most discussions about the term "Old School RPG", it seems most define it in two ways:
1) dungeon crawl hack and slash AND/OR
2) simple, quick game system
The two aren't necessarily mutually exclusive, but sometimes a debate/discussion about "Old School RPG" can get confusing when one party means the former and another the latter.).
Very good points-- particularly about the potential confusion.
In fact, I wouldn't really have imagined 2) to be a feature of "old school RPG". (In hearing the term "old school RPG" what I think of first and foremost is AD&D, which had three books (Player's Handbook, Dungeon Master's Guide) as part of the *basic* rules with a few other books issues thereafter (Fiend Folio, Dieties & Demigods, etc.),and just oodles of charts and tables throughout the Player's Handbook and DMG. Then again, maybe I'm wrong in considering AD&D "old school"? Does one have to go back to the original "Greyhawk", "Blackmoor", "Eldritch Wizardry" Supplements to be "old school"?
The games linked in the OP all seem to define themselves more in the second way--in how easy and fast their OGL d20 fantasy systems are.
I saw that in the copy for a few of them.
I also saw that the cover art for Swords & Wizardry depics a group of adventurers in a subterranean setting (obviously a "dungeon" or "ruin" of some sort) clambering over skeletons to get at some treasure. OSRIC shows other adventures-- again, in some grand Great-Hall-of-Moria like dungeon setting fighting a dragon. Labyrnth Lord shows a pair of adventureres-- again in a dungeon-- fighting some pig-faced orcs while a menacing spider loomsoverhead. While one should perhaps not judge books by their cover, I would say that the images on these are definitely screaming "dungeon crawl".
[minor edits to remove typos, extraneous phrases]