I thought that GPL licenses are meant for commercial use too http://www.gnu.org/licenses/gpl-faq.html#DoesTheGPLAllowMoney
Yes and no, yes someone could sell binaries + source legally. What they can't do is take your GPL'd source and make it their own proprietary source. Any modification they would do to the source would need to be distributed in source form along with any binaries.
In the practical sense, why would anyone buy the product that you are giving away for free? Any attempt, using a modified codebase, could simply be countered by incorporating the modifications into your codebase that you continue to give away for free.
An honest person has no need to pay, and a dishonest person has no desire. So technically yes, practically no.
Note that this is the flip side of the 'using GPL for commercial software' situation. In that situation, the only reason you get income is because you are the author. That is similar to a shareware type of situation, or even a 'donation' situation. Simply honest people doing the honest thing.
PS: Don't fall into the trap of trying to protect your code and binaries from dishonest people, you can't. Even closed source commercial efforts are subject to piracy and reverse engineering.
PS 2: CC BY-NC-ND license may possibly be applicable, but I hesitate to recommend it for three reasons; it is not intended for software, it rests upon public domain as a foundation, and finally, as far as I'm aware, it hasn't been subjected to the same degree of legal tests as GPL thus I don't place quite as much confidence in it.