@Andreas Nurbo - what @Jeffro said, GPL is copyleft and you have to publish the source code under the license (and most copyleft licenses) if you distribute the product, an app is a prime example of this: a distributed product that's made available for people for free or as a purchase. http://en.wikipedia.org/wiki/Copyleft

To be clear though, Pressgram doesn't break the GPL since it's code was not derived from any work that was copyleft. The decision to go with copyleft or not is a personal one and one that John is entitled to, but of course everybody has differing opinions on what the right way to go is.

Personally I'm excited to try it out, but wish it was GPL so it would help move the WP app space forward instead. :)