Objective-C has advantages of simplicity and optional dynamic types, neither of which is an attribute of C++. A lot of people don't realize that Objective-C is part of the GCC. So the compiler and library are available for Linux, Windows, and other Unix in addition to Mac OS X.
The language also has a reflection interface in pure C, so integrating scripting languages into Objective-C applications is a snap compared to C++ or even C. You don't have to generate stubs per API. Just call the reflection API dynamically.