He's not obligated to provide the SDK license, nor is he obligated to provide access to the AppStore. He's obligated to redistribute the GPL'd source code which he is. Hell, he could charge another $2.99 for the ability to download the source code if he wanted and that's all perfectly fine. Also, you are seriously confusing the concept of the why GPL'd source code is free. It's not free as in there is no cost. It's free in that you will always have access to the source and the ability to modify it as you see fit, so long as you also extend that freedom on to others.
Just because it's GPL does not mean it's also $0.00.
The submitter has done absolutely nothing wrong, and the original dev shouldn't have released the source under the GPL if he felt that the app should never be charged for. He should have released it under a non commercial license that explicitly restricted the sale of the software.