1971: Guidon Games publishes Gygax and Perren's "Chainmail" rules for tabletop miniatures wargaming
1974: D+D ("original" or "OD+D"), first TTRPG and ancestor of modern d20 RPGs, by Gygax's TSR company
1975: TSR acquires Chainmail from Guidon
1975: Greg Stafford's "White Bear and Red Moon" strategic boardgame establishes the Glorantha setting
- WB+RM was not a TTRPG; more similar to strategic map-based box games like Risk and Civilization
1975-6: TSR's "Boot Hill", "Metamorphosis Alpha": non-fantasy spinoffs of Chainmail / D+D d20ish ideas
1977: OD+D branches into "Basic" (aka "Holmes Basic") and "Advanced" D+D lines
1978: Stafford's Chaosium company launches "Runequest" to support Glorantha-centered TTRPGing
- RQ's d100 system is a major departure from D+D's character levels, classes, spell slots, etc.
1980: Chaosium releases "Basic Roleplaying" as a standalone rules booklet in RQ 2E boxed set
1981: Chaosium's "Stormbringer", "Call of Cthulhu"; first spinoffs in the RQ d100ish family
1984: Avalon Hill licenses Runequest, distributes 3rd Edition sans Glorantha as standalone fantasy TTRPG
- Very few non-Glorantha accessories emerge to support AH's "Fantasy Europe" setting
1985: Gygax ousted from TSR
- Corporate raider CEO Sharon Williamson burdens TSR, licensing her own family's moribund Buck Rogers IP
- waters down D+D reputation with interminable flood of low-quality accessories
1993: WotC (Wizards of the Coast) transforms the industry with "Magic: The Gathering" trading-card game
1994: Avalon Hill vs. Greg Stafford stalemate over Runequest 4E development
1997: WotC acquires insolvent TSR, including D+D, at fire-sale value of $25M
1997: AH / Chaosium connection dissolves, leaving RQ in AH's hands and Glorantha with Chaosium
- Chaosium's license to Michael Moorcock's "Eternal Champion" IP also lapsed around here
1998: Hasbro acquires Avalon Hill, and the Runequest game with it, for $6M
- Most of that value is in AH's popular boardgames like Diplomacy, not Runequest
- Glorantha is still Stafford/Chaosium's IP; non-Glorantha RQ community is almost nonexistent
1999: Hasbro acquires WotC for $325M. Most of the value is in Magic: the Gathering, not D+D.
Also 1999: Hasbro lets the Runequest trademark lapse entirely
2002: "Basic Roleplaying: The Chaosium System" (BRP 3E)
2003: Stafford boots up a new company, Issaries Inc., to reclaim the Runequest trademark
2004: Chaosium launches a series of BRP booklets, reproducing RQ 3E sans trademarked elements
2006: Mongoose Publishing licenses the RQ trademark to publish "Mongoose Runequest" (MRQ)
- First RQ derivation published under Open Gaming License (OGL)
2008: "Basic Roleplaying: The Chaosium System" (aka Big Gold Book): the 2004+ booklets in one volume
2009: Mongoose releases Runequest II as a luxury leather-bound updated edition
2011: Mongoose abandons the RQ trademark; OGL allows publication to continue under "Legends" brand
2012: The Design Mechanism publishes Runequest 6E
2016: TDM abandons the RQ trademark, continues publishing rebranded as "Mythras"
2018: Stafford rejoins Chaosium, launches "Runequest: Roleplaying in Glorantha".
2023: Chaosium "Basic Roleplaying: Universal Game Engine": streamlined, harmonized update of 2008 ed.
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Among current branches from original d100ish BRP/RQ, 2018 Runequest is probably the most popular.
Warhammer FRP also a branch of the d100 TTRPG family, and might actually have a larger player base.
BRP is a third-runner-up, then Mythras. The mechanical distinctions are minor and blurry between the current incarnations of RQ and Mythras; many fans are actually playing hybrid rulesets and any popularity contest there has to take into account units sold vs. a likely large sector of players freely using open digital reference resources.
"Magic World" is still occasionally mentioned, but as a Michael Moorcock "Eternal Champion" flavored subfamily which IP license is long lapsed, its player base is basically folded back into the BRP rollups.
Hon.mentions: Revolution d100 (2016); OpenQuest (2007, 3E 2021)
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d100 vs. d20 systems, and where it matters
D+D is by far the best-known game in the "d20" family. Why d20, because most chance-driven outcomes in the game are resolved by roll of a 20-sided die. Easy things are represented by a low "Difficulty Class" (DC) number, harder things have higher DCs. For example, a crude key lock might be represented by a DC 5 lockpicking difficulty - more of a speed bump than a serious challenge to a master thief. Building a character who's good at something means picking build options that let you add lots of modifiers to the skill rolls pertinent to that something: for lockpicking, high Dexterity gives a higher modifer to rolls for picking locks.
A character attempting to hit an opponent in combat is just a form of this skill-vs.-DC calculus: the target's Armor Class is a Difficulty Class, hopefully you have lots of modifiers to add to your Attack Rolls to help exceed the target's Armor Class.
Bottom line: in d20 systems, you generally want to roll high
Most d20 systems embed the idea that the highest possible roll, 20 before any modifiers on the d20, is an automatic success. (And/or maybe a "critical" hit dealing extra damage or impairing the foe in some way.)
Even non-hobbyists often recognize the idea of a "Sword +1". It lets you add 1 to your attack roll (on top of whatever other modifiers due to high Strength, character level, etc.)
In d100 systems like Runequest/BRP, skills are represented by a number that you have to roll under on d100 to succeed at a thing. For example, a starting-level hunter/warrior might have a Spear skill of 25. When the player wants the character to make an attack with a Spear, they roll d100 and if they roll 25 or under then they score a hit. The math feels a little nicer for folks who grasp odds in terms of "percent chance": the character has a 25% chance (1-25 on d100) to wound a foe with their Spear.
:: in d100 systems, you generally want to roll low
Where D+D's "natural 20 is a critical hit", in Runequest a very low roll is a crit.
Instead of adding the bonus to the roll with D+D's Sword +1, in RQ you'd add the bonus to the skill number you're trying to roll under.
Instead of abstracting character progression in terms of defeating encounters to reap "experience points" that count toward "leveling up" a general "proficiency modifier" whether the character actually uses a skill in session play or not ... d100 systems pose opportunities for characters to use skills, and only "level up" the skills they actually use. It makes for a more tailored and granular character-evolution experience.
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While I cherish memories of the Runequest sessions I played in the early-mid 90s, I think Glorantha is a weird niche setting with more lore than most medium-casual players want to have to digest just to understand their characters' values and motivations. So if I want to adapt a classic adventure like "Keep on the Borderlands" to familiarize D+D vets with d100, I think it's going to be via a generic derivative like Mythras - not trying to run a starter-level Glorantha scenario faithfully to that community's lore base.