I’ll plug my project inf7 – facilitating the use of an external editor is one of the reasons I wrote it. It’s a command-line program that can compile a project, translate the project index to straight HTML viewable in any browser, and, on successful compilation launch an interpreter running the game or on failure, a browser showing Problems.html. Other than the skein, I don’t think there’s any significant IDE functionality missing. It’s in ruby; once you’ve installed that, I would expect it to be straightforward to install and use on a Mac (though I haven’t tried it).
All that said, while I could recommend it to a sole developer, it would probably be a nuisance to write up installation instructions for a multi-platform classroom of students and to train them in how to use it. But I thought I’d offer it up.