Modern technology allows for computers to run on multiple processors. So like, say you had a computer, you could build it with a motherboard running duel, or even quad processors.
The problem with this, is generally software isn\'t designed to send one set of operations to one processor, and another set of operations to another processor, hence limiting the use of multiple processors. You have to build the program to do this.
I\'m not sure how the programming works in this case, but if CrystalSpace or PlaneShift did this, they would have to restructure the core code, which would be, my guess, very time consuming.