Let's look at the RPG products actually offered for Free RPG Day in Print - which means we cross off the retailer shirt, the dice tower and the Chessex and Q Workshop Dice. Which brings the 16 offerings down to 12.
The Cosmic Patrol Quickstart is a left over from last year and the Tuese'al Quickstart is only per box, so it's presence is negligible. If we remove them from the count, we really have 10 products being offered in print and new.
Of those 10, 4 are solidly OSR, and as I consider Tunnels & Trolls to be OSR, it's actually 5 out of 10.
"Hall of Bones" for Swords & Wizardry
"Better Than Any Man" for LotFP's Weird Fanyasy
The DCC / XCrawl Double Adventure from Goodman Games
"A Pot of Broken Bones and Halfling Broth": for Castles & Crusades
The Minotaur for Old-School Essentials
*Requirements:* Minimum STR 9, Minimum CON 9
*Prime Requisite:* STR and CON
*Hit Dice:* 1d10
*Maximum Level:* 8
*Armor:* Leather, including shield...