Freebooter takes OD&D and divorces it from elf game worlds and places it in the golden age of piracy. It was created by Night Owl Workshop. I've talked about a few NOW releases before (Guardians and Beasties).
The rules are very similar to OD&D but not identical. That being said, it's close enough. The back cover mentions 4 classes and in the next bullet mentions the optional Bokor class. I think this should have been combined, because the optional class is the fourth. The rules are complete. You get character creation, how to play, classes, equipment, and ship combat rules. Much of the book is devoted to the setting (the Caribbean during the golden age of piracy).
Since this is set in the real world, there is no bestiary, per se. Instead combat stats are given for various human antagonists and allies as well as animals (though some of them lean towards the fantastic). There are some interesting random tables. A nautical appendix N is presented and the book ends with the optional Bokor class and magic associated with it.
There are a few typos and one big mistake a noticed. The Target Number 0 chart on page 36 lists classes from Raiders of the Lost Artifacts, another Night Owl Workshop game, instead of the classes from Freebooters.
This is a fun book. While you could definitely just run a game straight out of the book, this is a perfect pirate sourcebook for White Box. That's why I bought it and I don't feel disappointed.
You can buy a print version from Lulu or get the pdf or print version from OBS.