"What is GORE?
GORE uses Open Game Content and newly presents algorithms from 80s role-playing games to produce a generic role-playing game in the tradition of old-school percentile-based games. GORE follows a trend that's been going on within the last few years in pen-and-paper games, that is, making material available to publishers to encourage competition and the contribution of high-quality gaming material to the market."
This game, along with several others, represent a special class of RPG called a "Retro-Clone". The other RPGs that fall into this category are:
Swords & Wizardry