I use Resin for development on my OSX machine. Its fantastic.
Their licensing is not 100% free. You would need to pay for it if you use it in a production environment, but if you only use it for development, it is entirely free.
You can pretty much follow the unix setup instructions, and get resin running. I didn't run into any OSX specific problems when setting up Resin.
Feel free to ask if you have any questions or problems.
-tim