You can build commercial anything with GPL. GPL isn't anti-commerce. So, you don't need anyone's permission to do commercial things with GPL software.
If a company says, "here's this under GPL, but if you want a commercial license, pay us specially" they are being deceptive. You don't need a special commercial license. GPL allows any commercial activities, period.
You don't need to relicense in order to use the software commercially or to do any other use. The GPL respects freedom 0: freedom to use the software as you wish in whatever way you wish.
When you ask Apple to distribute and sell a program in their store, they require several things from you as a developer.
1: They require you to agree and follow apple's app store policy for developers. The policy include a long list of actions which you can't do as a developer, including using software licensed under GPL.
2: Apple will add during distribution their own app store copyright license to govern the use of the program. Apple requires that the developer provide legal permission for this, and will refuse to distribute if there is license incompatibility or other problems regarding copyright. If a developer sub-license other peoples copyrighted work like code, images, video or content in general, it is the developer that must shoulder any and all responsibility. If the license require that you can not add additional restrictions (See Sublicensing field in https://en.wikipedia.org/wiki/Comparison_of_free_and_open-so...) then the developer is required to seek additional permission since then the license is not compatible with Apple's license.
In general, distributing other peoples work is tricky if you want to add a new license on top. Make sure you got permission, and if uncertain, ask the author explicitly. Judges seems to like when people explicitly seeks permission rather than relying on an interpretation of a license text.
The GPL does not prevent you in any way from distributing an iOS application and charging money for it (provided that you make the source code available for that part of the app that is a derivative of the GPL'd work), it is just that in practice Apple will censor applications that contain GPL'd code from their App Store.
That is entirely Apple's decision to make; they reportedly also censor apps that display nudity etc. and I would not be convinced by an argument that nobody can make money with pictures of nude people.
I never said nobody couldn't make money off GPL, I said a lot of the times GPL/AGPL will mean in practice you cant use them comercially and the author expects this and offers you a custom license - which both fails the FS ideology and is the only rational use case for the license IMNSHO.
Well, the GPL allows the publication of iOS apps. Apple is the one who doesn't allow GPL to be included in the app store.
You might as well see a restaurant that refuses to serve people who wear headscarves or something and then say that headscarves restrict your dining options. It's completely backward attribution of the problem.
You can use GPL alongside any other license at all, including proprietary. You have zero obligations under GPL for whatever you want to do with software privately. The only obligations relate to keeping the terms for others when you distribute the software to them.
If a company says, "here's this under GPL, but if you want a commercial license, pay us specially" they are being deceptive. You don't need a special commercial license. GPL allows any commercial activities, period.
You don't need to relicense in order to use the software commercially or to do any other use. The GPL respects freedom 0: freedom to use the software as you wish in whatever way you wish.