Medium size Windows project port to Objective C for Mac OSX

We have a fully functional live windows project that is launched with some major clients in the US, one being a top 10 internet site. The product is a new type of advertising platform that offers downloadable titles within an installer. Basically, we need an Objective C port of our C++ code for Mac OS X that operates exactly the same as our current version. Some examples of the operation: * Basically a very slimmed down version of nsis * Parses json * Displays remote pages within dialogs * Executes system level commands * Checks registry keys/indicators of installations * Checks search settings * Plugin detection The downloadable software has two primary actions: 1. Detection of currently installed titles/settings/etc 2. Parse and display of json into dialogs The programmer will have access to the C++ code to assist with the port (which should obviously make this much easier).