There’s an article by the Free Software Foundation as to where, what, and why the GPL is in conflict with Apple’s T&C:
http://www.fsf.org/news/blogs/licensing/more-about-the-app-store-gpl-enforcement

While the article is a bit dated, and it focuses on version 2 of the GPL, the conflicting statements remain in GPLv3, (which is even stricter in its formulation of copyleft) and the App Store T&C.

Because the GPL does not allow overriding its copyleft, your addition that one might use the code in App Store Apps is moot. So you’re basically left with any combination of the following options:

• Pull your own App from the Store, because you cannot comply with the license you’ve chosen for your own code. (Probably the last thing you want…)
• Switch to a liberal open source license (like MIT, BSD, etc.).
• Dual license your code. (Then again: why keeping the GPL at all, if one always needed the other license to do something with the code, anyways?)
• Try petitioning Apple to create a DRM-free section on the App Store, or an alternate distribution channel (perhaps similar to Gatekeeper on OS X) for apps that cannot comply with the current T&C. (Unlikely to succeed but if it did, it would be great.)

This list is probably incomplete, but hey…

I've downloaded this the other day running Xcode 4.2

on bitmapatlas.m
I'm getting semantic errors ..assigning property with readonly attribute is not allowed and it points to this piece of code

// Apply label properties
    fontChar.opacity = self.opacity;
    [fontChar setColor:color_];
}

any ideas whats up with this?

Here is the crash while launching app.

*** Assertion failure in -[UIApplication _runWithMainScene:transitionContext:completion:], /BuildRoot/Library/Caches/com.apple.xbs/Sources/UIKit_Sim/UIKit-3600.6.21/UIApplication.m:3680
2017-01-21 15:49:34.610 AlphabetBlocks[4425:138444] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Application windows are expected to have a root view controller at the end of application launch'
*** First throw call stack:
(
0 CoreFoundation 0x036c2bf2 __exceptionPreprocess + 194
1 libobjc.A.dylib 0x030d6e66 objc_exception_throw + 52
2 CoreFoundation 0x036c6d12 +[NSException raise:format:arguments:] + 130
3 Foundation 0x0028daf4 -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:] + 94
4 UIKit 0x006b2870 -[UIApplication _runWithMainScene:transitionContext:completion:] + 4000
5 UIKit 0x006d37d5 __84-[UIApplication _handleApplicationActivationWithScene:transitionContext:completion:]_block_invoke.3129 + 53
6 UIKit 0x006aecc2 -[UIApplication workspaceDidEndTransaction:] + 172
7 FrontBoardServices 0x051bb1a5 __37-[FBSWorkspace clientEndTransaction:]_block_invoke_2 + 59
8 FrontBoardServices 0x051bacc5 __40-[FBSWorkspace _performDelegateCallOut:]_block_invoke + 49
9 FrontBoardServices 0x051e466c FBSSERIALQUEUE_IS_CALLING_OUT_TO_A_BLOCK + 23
10 FrontBoardServices 0x051e44cd -[FBSSerialQueue _performNext] + 166
11 FrontBoardServices 0x051e48ad -[FBSSerialQueue _performNextFromRunLoopSource] + 52
12 FrontBoardServices 0x051e3cc7 FBSSerialQueueRunLoopSourceHandler + 29
13 CoreFoundation 0x03661edf CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION + 15
14 CoreFoundation 0x03645fa7 __CFRunLoopDoSources0 + 519
15 CoreFoundation 0x03645434 __CFRunLoopRun + 1124
16 CoreFoundation 0x03644d5b CFRunLoopRunSpecific + 395
17 CoreFoundation 0x03644bbb CFRunLoopRunInMode + 123
18 UIKit 0x006ad33b -[UIApplication _run] + 542
19 UIKit 0x006b3ff3 UIApplicationMain + 148
20 AlphabetBlocks 0x00050cf0 main + 128
21 libdyld.dylib 0x04a94799 start + 1
22 ??? 0x00000001 0x0 + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException