Actually no. This is a common misconception. The GPL does *not* forbid selling GPL software! The requirement is that you have to publish *all source* and especially modifications you make.

On Oct 5, 2013, at 12:33 AM, pd-list-request@iem.at wrote:

From: "Pagano, Patrick" <pat@digitalworlds.ufl.edu>
Subject: Re: [PD] Legal restrictions for apps
Date: October 4, 2013 1:37:21 AM GMT+08:00
To: Simon Wise <simonzwise@gmail.com>
Cc: pd-list <Pd-list@iem.at>


There was quite a lot of discussion on the supercollider list about this too. Everyone is quick to share that you can't sell it. I don't want to sell anything I want to use the programs for my own use on a tablet, plain and simple. 

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Dan Wilcox
@danomatika