The Horizon Framework

Horizon is an open source tabletop roleplaying framework. It aims to be very simple at its core, bound by only a few mechanics, and easily malleable for designers and GMs alike.

It runs on a D6 success/failure system, allows the addition of custom skills and features, has rules for crafting, pets, combat, and so much more!

Horizon uses a license that is very similar to the MIT license, but altered for relevance, and made irrevocable and perpetual as to be used in part or entirely by game designers as they see fit.