RPJ: A Free, Open Tabletop Roleplaying Game System

RPJ. Where to begin?

What Is It?

RPJ is a free (gratis) and free (libre) roleplaying game system. It is based on the 4d6 roll, which generates a nice bell curve centered around 14, and features a very, very simple core set of rules, along with a robust list of optional mechanics for various situations.

At the bottom of this page, you can find links to the Core rulebook, whatever first-party modules I have produced, and perhaps someday links to third-party RPJ projects.

The Name

Roleplaying games are RPGs. My name is Jay. Ergo, RPJ.

The Beginning

The year: 2008. The place: Rochester, New York. Your intrepid author, a young college student at the time, was griping about having to buy sets of dice to play tabletop games. “Why,” he wondered, “do I need dice, when I have a pocket full of perfectly good, perfectly random coins?”

This absurd non sequitur, plus a hundred hours or two but dedicated work in the way college students can afford, yielded a Core rulebook and a Fantasy setting. By this time, your author was living with a bunch of people who were all for tabletop roleplaying. A subset of them were even cautiously in favor of trying a weird, untested homebrew system whose existence was justified only by the aforesaid absurd non sequitur.

The fools.

RPJ, in its original form circa 2010, was not a good game. It was clunky, slow to play, and in some cases asked players to flip 40 coins for a single skill roll. This was not ideal. To their credit, those original players stuck with the game, and indeed looked upon it with a great deal of enthusiasm. In spite of their gamemaster (your author again) being as new to gamemastering as he was to game design, and juggling the usual session preparation with minor, or in some cases wholesale, changes to the rules, they nevertheless returned to the table week after week, and were instrumental both in cleaning up some of the rules and improving the feel of the setting1.

So concluded the first chapter of RPJ history.

The Second Module

The year: 2011. After hard work incorporating the lessons from the first RPJ campaign and further hard work writing a new module, your intrepid author unleashed RPJ Sci-Fi upon his unsuspecting players.

RPJ Sci-Fi, a near-total ripoff of Warhammer 40,000: Rogue Trader, and the associated version of RPJ Core were much streamlined over the state of affairs at the time of RPJ Fantasy. The first really playable RPJ game, RPJ Sci-Fi introduced and tested the Fire and Movement optional core mechanic in RPJ Core, and further refined rules on skill rolling and character creation.

Eventually, RPJ’s testers and author graduated and left left Rochester. Experiments in remote play with 2011’s technology did not go well.

So concluded the second chapter of RPJ history.

Recent History

The year: 2018. The place: Pittsburgh, Pennsylvania. Your intrepid author, having found local friends with a fondness for tabletop gaming, gets back into the hobby a bit, and inspiration strikes. Rewrites of RPJ Core and RPJ Sci-Fi to ditch the coin-based gameplay in favor of 4d6 begin.

A former RPJ player and your intrepid author now work in the same office, and in the course of daily chit-chat, roleplaying games came up. In particular, Larry Correia’s Gritty Cop Show RPG. It was decided that an RPJ cop drama module should be written.

That about brings you up to speed.

Available First-Party Modules

All of the currently-public RPJ first-party rulebooks are available gratis. They may or may not be libre. Those which are bear an indication thereof, along with the terms under which they are available. I and/or other authors of first-party modules retain the copyrights to unmarked rulebooks.


Prerelease rulebooks are subject to change at any time. I don’t make a detailed effort to keep change logs, much less post them, for prerelease rulebooks. I will do my best to note when they change here, but that’s not a promise.

  • RPJ Core (libre, CC BY-NC-SA)
    RPJ Core is the core rulebook for RPJ, and contains information on attributes, characters, skills, and combat, all of which you may use or ignore at your discretion.
  • Police Cops
    Police Cops is a gritty, hard-charging police drama module, which uses a simplified version of the RPJ Core ruleset for faster character creation and quicker play. It is written with one-shot games in mind, but has some support for longer campaigns.


Released rulebooks are subject to less frequent changes and have version numbers.

Unfortunately, no currently-available RPJ rulebooks are at the phase where I’m willing to call them ‘released’. Sorry.

Third-Party Projects

If you have one cooking, let me know, and I’ll link to it here.

Other Resources

The Conclave has an RPJ forum.

  1. If you’ve read the fantasy stories here, you’ve seen some of the fruits of their aid. 
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