Superworld was in fact Champions, 2nd ed system for managing powers tacked on BRP.
It was one that part badly done and prone to breaking (we tried and succeded successfuly at that time when we were quite powerplayers):
With champions, the active cost is divided by 1+(sum of limitations) to get the real cost, which drives a reduction of efficiency each time you add a limitation.
With superworld, you get a price break of n 6th of the price for each limitation, which means that if you get 6 1/6th limitations (or 3 1/3rd limitations), the power cost becomes ... ZERO, and you could get all the powers of the book at an infinite level for free.
At that time, a friend of mine discovered that. We were already more inclined to used Champions and, in addition with the lack of support from Chaosium, that was the crippling blow. We stopped using Superworld because some players were unstoppable.
Another problem was that the number of power points was to be equal to the total sum of characteristics, which could drive to stupid characters, just to have the right amount of power points.
Runequestement votre,
Kloster