Hey board,
I've decoupled the Ruby/Gosu .app wrapper for OS X from Gosu itself and uploaded it as its own project:
https://github.com/jlnr/ruby_app/releases/tag/v0.7.48It still includes Gosu, but not forcibly so - it's just another gem that the app happens to contain. It should be pretty easy to use this skeleton for any Ruby gamedev library (if there were any left).
All components have received a version bump, and Gosu is now fully compatible with Ruby 2.0 except on Windows.
The repository looks very WIP, but it's mostly the documentation that's missing, and some helpers to make it even easier to build this beast.
If anyone has a Mac that's running 10.9, 10.7 or Intel 10.5, please let me know how the app is working for you.