If it isn't obvious, GPL is an attack against proprietary computers and against the corporations that have been trying repeatedly over decades to bottle-up and monopolize the computer revolution.
No matter how idealistic any large group of young hackers will want to be, fiduciary duty will always trump everything when you play with business. You can love the GPL as much as Stallman himself, but when you're grasping for any edge you can find over your competition, you'll think twice before shipping her a tarball of your source.
Reusing GPL'd code forces developers to in turn release their code; more free licenses don't have this effect.
Anyway, not to play thread police, it just seemed to me that it was veering off into another direction. I'm cranky in the mornings!
Contrast this with proprietary software.
There are restrictions for developers, namely that you can't link GPLed code to non-GPLed or GPLable code, and that you can't close the source.
Liberal licenses are easier on developers, but they don't guarantee that the source will remain open. Software is ubiquitous nowadays, and most appliances use closed source software of unknown quality and probity. There's spyware in every cell phone, for example.
More GPL makes a better world, overall.