Basic Role-Playing, or BRP, is the name of the "generic" form of the fantasy-oriented RuneQuest role-playing game rules. A percentile skill-based system, BRP was used as the basis for most of the games published by Chaosium, including Call of Cthulhu (RPG), Elfquest, Stormbringer (aka Elric!), Hawkmoon, Superworld, Nephilim, and Ringworld. Pendragon (acquired in 1998 by Green Knight Publishing), while related, has sufficiently different mechanics that it can only be seen as a separate system. The BRP standalone booklet was first released in 1982 as part of the Worlds of Wonder boxed set. Greg Stafford and Lynn Willis are credited as the authors.
At least one non-Chaosium game has used BRP for its core rules. Other Suns, published by Fantasy Games Unlimited (FGU), used them under license. In addition, Corum, a supplement to the Stormbringer rules, was published in the fall of 2001 by Darcsyde Productions. BRP was used (through a special arrangement with Swedish gaming guru Fred Malmberg) as the base for the highly successful Swedish game Drakar & Demoner from Target Games.
BRP was conceived of as being a sort of genre-generic engine around which any sort of RPG could be played, much like GURPS and the D20 system have become today. In order to underscore this, Chaosium produced the Worlds of Wonder supplement, which contained the generic rules and several specific applications of those rules to given genres. Superworld, specifically, began as a portion of the Worlds of Wonder product.
Although similar in a general way to other generic systems such as GURPS, Hero System or Savage Worlds, BRP is also quite different. Each incarnation of the BRP rules has changed or added to the core ideas and mechanics, resulting in generally compatible games that also provide a slightly different tone or feel to them, or which have slightly different rules interpretations. For example, in Call of Cthulhu, skills may never be over 100%, while in Stormbringer skills in excess of 100% are encouraged for those who follow Law.
BRP was developed from a core set of attributes very similar to the original Dungeons and Dragons (D&D). So Strength, Constitution, Size, Intelligence, Power, Dexterity and Charisma (or Appearance) replaced the D&D norms. From that was evolved a structurally simulationist system. Therefore hit points, which increase with experience in D&D were based on the average of Size and Constitution and were functionally stable for the life of the character. Skills, using a d100, rather than the D&D d20, were used to simulate the way that people learn skills. Experience points were replaced by an experience check, rolling higher than your current skill on a d100. This created a learning curve that levelled out the higher a skill was. The Resistance Table, in which two attributes are compared and a chance of success read from a table, is the ugly duckling of the BRP system. It is potentially an entire system mechanic on its own and yet many say it sits oddly with the existing skill system.
Armour, which had been merged with defence in D&D was broken out. The act of parrying was a skill, the ability of the armor to absorb damage was a separate function. The last major element of many BRP games is one that is shared with Tunnels and Trolls (T&T), which originated this, which is that there is no difference between the player character race systems and the monster or opponents. By varying ability scores the same system is used for a human hero as a trollish villain. This approach also led quickly, as it did in T&T, to players often playing a wide range of non-human characters and game worlds that were deeply pluralist.
The core rules were originally written by Steve Perrin as part of his ground-breaking game RuneQuest. It was Greg Stafford's idea to simplify the rules (eliminating such things as Strike Ranks and Hit Locations) and issue them in a 16 page booklet called Basic Role Playing. Over the years several others, including Sandy Petersen, Lynn Willis and undoubtedly many more, contributed to their final form.
In 2004, Chaosium published the Basic Role-Playing Players Book and Magic Book in monograph format, a very quick and cheap printed format, in order to assert their copyrights in the run-up to the publishing and distribution of essentially the 3rd Edition RuneQuest rules under the Basic Role-Playing name.