NSObject category to get subclasses

NSObject+Subclasses.h

#import <Foundation/Foundation.h>

@interface NSObject (Subclasses)

+ (NSSet *) subclasses_xcd;

@end

NSObject+Subclasses.m

#import "NSObject+Subclasses.h"
#import <objc/runtime.h>

@implementation NSObject (Subclasses)

static inline BOOL IsSubclassOfClass(Class subclass, Class superclass)
{
	for (Class class = class_getSuperclass(subclass); class != Nil; class = class_getSuperclass(class))
	{
		if (class == superclass)
			return YES;
	}
	return NO;
}

+ (NSSet *) subclasses_xcd
{
	static void * SubclassesKey = &SubclassesKey;
	NSMutableSet *subclasses = objc_getAssociatedObject(self, SubclassesKey);
	if (!subclasses)
	{
		subclasses = [NSMutableSet set];
		
		unsigned int count = 0;
		Class *classes = objc_copyClassList(&count);
		for (int i = 0; i < count; i++)
		{
			Class class = classes[i];
			// Do not use -[NSObject isSubclassOfClass:] in order to avoid calling +initialize on all classes
			if (IsSubclassOfClass(class, self))
				[subclasses addObject:class];
		}
		free(classes);
		
		objc_setAssociatedObject(self, SubclassesKey, subclasses, OBJC_ASSOCIATION_COPY);
	}
	return subclasses;
}

@end

Hi, may i know if the licensing for the above piece of code? Are the code granted open source with no restriction to the rights of use, copy, merge, publish, distribute, sublicense and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.