The GPL says “you can sell this if you want, but whoever you sell it to can still do whatever they want with it, subject to the same terms.”
CC-NC says “you can't do whatever you want with this”
Which isn't to say that you're wrong to use whatever license you like, just that it's very much not similar in spirit to the GPL. Protecting the right of others to make derivatives of the thing being licensed is, in fact, the entire point of the license.
