GUMSHOE, FATE, Forged in the Dark, Dungeon World, Quest, and Trophy are all available under CC BY licenses. Many of those are fairly popular (if you don’t compare them to D&D) — six figure Kickstarter revenue, for example. Creative Commons has been a reasonably common choice for game designers who want open content for a decade or so.
GUMSHOE, FATE, Forged in the Dark, Dungeon World, Quest, and Trophy are all available under CC BY licenses. Many of those are fairly popular (if you don’t compare them to D&D) — six figure Kickstarter revenue, for example. Creative Commons has been a reasonably common choice for game designers who want open content for a decade or so.