RetroQuest (d100 compatible)

From the introduction:

RetroQuest uses Open Game Content and newly presents algorithms from 1980s role-playing games. The result is a role-playing system in the tradition of old-school percentile-based games. RetroQuest follows a trend in pen- and-paper RPGs which has emerged over the last several years, that is, making material available to publishers to encourage competition and the contribution of high-quality gaming products to the market. Most new language and presentation in RetroQuest comes from GORE™ and is Product Identity from Goblinoid Games, used under a free license. This product is compatible not just with GORE™, but also with any of several old-school games using a percentile-based system with similar algorithms.