SOE recently published an interesting overview of the Jedi expertise paths in Star Wars Galaxies. Information about the light and dark sides of the force are covered and it's a quite interesting read.
The expertise system gives Jedi a choice of the path they wish to follow in the universe of Star Wars Galaxies. Choose a side and your role as a Jedi with the Path tree in the expertise system, now with several new abilities added in Game Update 3.
Choose Your Path
The left side of the Path expertise tree represents the light side of the Force and the right side of the tree embodies the dark side. The light side centers on calm and forethought to improve defensive capabilities, while the fury and passion of the dark side focuses on offensive powers.
A Jedi stance is required for abilities on the left side of the tree, and a Jedi focus is required to use the abilities on the right side of the tree.
Jedi who are not completely taken over by one side or the other may still choose abilities of both sides. Although Jedi are free to choose between the two sides of the Force, abilities and passive bonuses cannot be used while in the opposite stance or focus.
Light Side of the Force
Through careful meditation and study of the light side of the Force, a Jedi can slow down enemies, increase damage and lightsaber skills, support his or her allies, and more.