I figured I'd let you know about the latest developments regarding Grasshopper (and other .NET plugins) for Rhino Mac.
Last week some of us from McNeel spoke with Miguel de Icaza (head of development of the Mono project) about running plugins that use Windows.Forms on Mono-Mac. The news is basically not good. Though it isn't terribly bad either.
The WinForms part of Mono is build upon the old Mac Carbon scheme. Rhino for Mac is build upon the new Mac Cocoa scheme. These two don't play well together. This means we cannot run Grasshopper without modifications on the Mac.
Miguel advised us to write a wrapper dll for UI elements that is hooked up to WinForms on windows and Cocoa on Mac, and this will allow Plugin developers to write plugins with a GUI that will run on both Operating systems. Development of these libraries will take months even with an experienced developer. And then I need to rewrite all the UI in Grasshopper. As you can probably imagine, this is not exactly trivial.