What's the long and short of it? Is there a version of the editor that I can use on Yosemite currently?
This particular thread never touched
Editor; it is dedicated to porting AGS
engine to OSX (as stated in the title).
Engine status: there is a Mac port by Wadjet Eye that can play games made with AGS 3.2.1 and lower. It is practically possible to update it to more contemporary version of engine, but it will take some work. Last time I heard about this, Janet Gilbert from WE wanted to hire programmer again to do this; also Nick Sonneveld mentioned plans to help them, but I do not personally track the progress in that area at the moment.
Editor status: there were
talks about moving to Mono (as Editor is a C# program), but number of Editor parts still have dependencies on Windows runtime libraries, and it is unknown if anyone works on this.
I also heard that you may run Editor on Mac using some wrapper, but I am not a Mac person, so cannot help you here.