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.

Directly below, you’ll find the list of available RPJ modules. A litte further down the page, you can read some on the history and motivations behind RPJ.

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.

There are no prerelease rulebooks available at present.


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

  • RPJ Core v1.0.0-beta14 (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 v1.0.0-beta3
    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.
  • RPJ Sci-Fi v1.0.0-beta13 (libre, CC BY-NC-SA)
    RPJ Sci-Fi is a space opera setting which is similar in concept to Warhammer 40,000 Roleplay: Rogue Trader, throwing in a unique Greek twist and a much smaller helping of grimdarkness. Players ply the space lanes in gargantuan jump ships, carrying freighters which carry the fruits of trade throughout an Empire which traces its lineage to Alexander the Great.

Why RPJ?

Good question!

It’s Open

Not only is the core rulebook licensed permissively, RPJ Sci-Fi is too. So too will be most other first-party rulebooks.

This means unprecedented flexibility for you, the gamemaster or module author. You can mix and match rules, systems, and setting elements however you like.

It’s Free

All of the currently-available RPJ material is available free of charge. This is a major improvement over ordinary for-profit RPGs, where the starting investment is at least two to three books.

Furthermore, you only need four six-sided dice, which you probably already have. Even if you don’t, you can get a set of 36 for $5 or so, and if you don’t have 4d6 lying around somewhere, you can hardly blame that on me.

It’s Generic

RPJ Core makes no assumptions about the genre of its settings, and as such can be used for any genre you can think of. It includes a variety of optional rules you can include or ignore at your pleasure, gives you the tools to build your own optional rules, and provides structure for integrating it all together.

It’s Complete

RPJ Core is a complete set of rules for roleplaying games, and the open content available in RPJ Sci-Fi and other, as-yet unreleased games provides you fertile ground for wholesale copying. Assembling a new, standalone RPJ-based game or RPJ setting does not take a major exercise in creativity, or won’t, once a wider variety of RPJ systems have been released.

It’s Tested

This is even more of a stretch than the previous heading, but I have played through some example combat and some example social encounters in RPJ, and found that the rules function about like I expect them to.

It’s Simple

“Ha!” my wife would no doubt exclaim, were she to read this page. Really, though, RPJ is fairly simple by the standards of tabletop roleplaying games, falling somewhere in between D&D 5th Edition and Pathfinder. The basic action is roll 4d6, add a skill level, add an attribute bonus.

It takes fewer dice than the old Star Wars d6 system or even D&D, plays more simply than GURPS, and comes with two (at present) ready-made modules.

Furthermore, first-party RPJ modules come with a selection of cheat sheets and automatic tools which ease the transition to RPJ from other roleplaying game systems, both at character creation and in moment-to-moment gameplay.

It Solves My Problems With d20 Games

Say you’re playing 5e, and you have a skill modifier of 5. That means your average performance is to pass a skill check with a DC of 15, which the 5e SRD calls ‘medium’. The thing is, you get to that average by evenly distributing your performances between 6 (very easy) and 25 (very hard). You’re just as likely to perform exactly at your level as you are to perform far above it, which seems wrong to me.

In RPJ, you roll 4d6, and when you roll multiple dice, you get a bell curve. Most of the time, you perform at your level, with the occasional push beyond your abilities or fumble beneath them—frequently enough to be narratively interesting, but not so frequently that the game becomes a story about your luck on dice rolls.

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 a hundred or so hours of 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. I’ve now put more than 2,000 hours into RPJ and related content. I hope it brings you a few minutes of joy.

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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