(1) “The GPL is a worldwide copyright license”
The FSF explains that GPL2 was written with reference to US law, and accordingly GPL3 will seek to “ease internationalization difficulties” in view of the “otherwise unsought ideal of the global copyright license.”
(2) “The GPL is the code of conduct for free software distributors”
As such, the FSF says its role is in the nature of “standard-setting”, or ‘best practices' definition”.
(3) “The GPL is the constitution of the free software movement”
The FSF notes that its primary goals are “social and political” not “technical or economic.” Accordingly, it may address measures that it sees as “harmful to freedom,” such as trusted computing and patents.
(4) “The GPL is the literary work of Richard M. Stallman”
As the author of the GPL, Stallman will continue to guide its evolution. It is interesting that this fact qualifies as a distinct “purpose” of the GPL, according to the FSF, -- i.e., for Stallman to preserve the integrity of the work as representative of his intentions.