Definition: "Gray Jedi," like "Dark Jedi," is a general term for Force-users who fall outside the two major orders, Jedi and Sith. While individual beliefs and practices vary, the existence of Gray Jedi presents a third major philosophy of the Force: that the dark and light sides both have merit, and that one can touch the dark side without becoming evil. This idea adds a sense of moral ambiguity to the Force in the Expanded Universe which is not present in the Star Wars films.
The first Gray Jedi appeared after the Jedi Council began to centralize and consolidate its power after the Great Sith Wars of 4,000 BBY. Some Jedi disliked the idea of a central Jedi authority rather than the decentralized local organizations that had been prevalent earlier, as well as new customs such as prohibiting marriage. Rejecting both the Jedi and the Sith, these early Gray Jedi used the Force on their own terms.
As the Jedi Council grew more powerful, however, the meaning of the term Gray Jedi grew watered-down, used to attack any detractors. For example, Qui-Gon Jinn was accused of being a Gray Jedi not for touching the dark side, but for his frequent conflict with the Jedi Council.
The use of both the dark and light sides of the Force potentially gave Gray Jedi access to powers not normally seen in traditional Jedi, such as Force lightning. Merely using these abilities did not make someone a Gray Jedi, however, since a few Jedi could access them through the light side of the Force.
To be considered a Gray Jedi, a Force user must touch the dark side but, unlike a Sith or Dark Jedi, not fall to it. Force users who simply deny the existence of the dark side are not Gray Jedi.
Gray Jedi Orders
Although a single, centralized Gray Jedi Order never existed, there are a number of organizations which follow Gray Jedi philosophies. Some directly split from the Jedi Order: for example, the Imperial Knights, sworn to protect and serve the Fel Empire. Others, like the Jensaarai, grew from a combination of Jedi and Sith teachings. Still others, like the Voss Mystics, developed independently from either major order.