A Permission Giver is someone who grants Permission.
The original Permission Givers, although not under that title, were Jay and Acacia, the Real World creators of the PPC. These two retired in 2003 and passed their Permission Giving powers on to GreyLadyBast, Miss Cam, and Thalia Weaver, three of their biggest supporters.
Since that time, Permission Givers have been selected in a number of ways. Some were chosen by the other Permission Givers directly. Others, notably the last few sets (starting with Huinesoron and Techno-Dann), were elected by the Board as a whole. There is no established mechanism for such an election—it's done on a case-by-case basis. The requirements for being chosen as a Permission Giver are a reasonable level of activity for a decent amount of time (currently six months, although longer is better), and a dedication to the PPC in general. At one point it was suggested that everyone who had been with the PPC for more than a year could automatically become a Permission Giver, but this idea was abandoned.
This is a list of those who are Permission Givers. Mind, however, that not all of these people are active.