Well, a wrapper is an API that really just mimics and then interfaces into another API.
Many people used to write Glide wrappers to get Glide games working with OpenGL and DirectX on the PC side.
What this would be doing is emulating the DirectX API on Linux/Mac systems and sit on top of GameSprockets (probably) and OpenGL under OS 9, and OpenGL under OS X.
This will mean 1 good thing: shorter port times of PC games, which may lead to not having to spend more than a month or so doing minor tweaks and tests. The majority of the time spent on larger PC -> Mac projects is the switch from DirectX to the MacOS APIs. If this is properly implemented, it could cut down on that time drastically.
