After code fix applied

UAAppDelegateSurrogate.m

#import "UAAppDelegateSurrogate.h"

@interface UAAppDelegateSurrogate()

@property (nonatomic, readwrite, copy) NSDictionary *launchOptions;

@end

@implementation UAAppDelegateSurrogate

@synthesize surrogateDelegate;
@synthesize launchOptions;

SINGLETON_IMPLEMENTATION(UAAppDelegateSurrogate);

/* this method is called the moment the class is made known to the obj-c runtime,
 before app launch completes. */
+ (void)load {
    NSNotificationCenter *center = [NSNotificationCenter defaultCenter];
    [center addObserver:[UAAppDelegateSurrogate shared] selector:@selector(handleLaunchNotification:) name:@"UIApplicationDidFinishLaunchingNotification" object:nil];
}

- (void)handleLaunchNotification:(NSNotification *)notification {
    //store the launch options for later use
    self.launchOptions = notification.userInfo;

    //swap pointers with the initial app delegate
    @synchronized ([UIApplication sharedApplication]) {
        id<UIApplicationDelegate> del = [UIApplication sharedApplication].delegate;
        /* note: although according to the docs [UIApplication setDelegate] doesn't retain, the 
         initial delegate does appear to be released (deallocated) when a new delegate
         is set, unless we retain it here */
        defaultAppDelegate = [del retain];
        [UIApplication sharedApplication].delegate = self;
    }
}

#pragma mark Message forwarding

- (void)forwardInvocation:(NSInvocation *)invocation {
    SEL selector = [invocation selector];

    if ([defaultAppDelegate respondsToSelector:selector] || [surrogateDelegate respondsToSelector:selector]) {
        //allow the surrogate delegate a chance to respond first
        if ([surrogateDelegate respondsToSelector:selector]) {
            [invocation invokeWithTarget:surrogateDelegate];
        }

        //forward to the default delate if necessary
        if ([defaultAppDelegate respondsToSelector:selector]) {
            [invocation invokeWithTarget:defaultAppDelegate];
        }
    }

    //otherwise trigger default behavior (usually throws NSInvalidArgumentException)
    else {
        [super forwardInvocation:invocation];
    }
}


- (BOOL)respondsToSelector:(SEL)selector {
    if ([super respondsToSelector:selector]) {
        return YES;
    }

    else {
        //if this isn't a selector we normally respond to, say we do as long as either delegate does
        if ([defaultAppDelegate respondsToSelector:selector] || [surrogateDelegate respondsToSelector:selector]) {
            return YES;
        }
    }

    return NO;
}

- (NSMethodSignature*)methodSignatureForSelector:(SEL)selector {
    NSMethodSignature* signature = [super methodSignatureForSelector:selector];
    if (!signature) {
        signature = [defaultAppDelegate methodSignatureForSelector:selector];
    } else {
        signature = [surrogateDelegate methodSignatureForSelector:selector];
    }
    return signature;
}

#pragma mark Other stuff

- (void)dealloc {
    RELEASE_SAFELY(launchOptions);
}

- (NSUInteger) application:(UIApplication *)application supportedInterfaceOrientationsForWindow:(UIWindow *)window
{
    // IPhone doesn't support upside down by default, while the IPad does.  Override to allow all orientations always, and let the root view controller decide whats allowed (the supported orientations mask gets intersected).
    NSUInteger supportedInterfaceOrientations = (1 << UIInterfaceOrientationPortrait) | (1 << UIInterfaceOrientationLandscapeLeft) | (1 << UIInterfaceOrientationLandscapeRight) | (1 << UIInterfaceOrientationPortraitUpsideDown);
    return supportedInterfaceOrientations;
}

@end