In the Mac space, the open source MacRuby project is intended to provide an optimized and integrated version of Ruby for Mac OS X and be compatible with Ruby programs. MacRuby leverages Apple's Cocoa technology, which provides an Objective-C-based programming environment for Mac OS X.

Concurrent programming, for managing multiple threads, is featured in the MacRuby effort via the GCD (Grand Central Dispatch) technology in Mac OS. "I think [GCD] is really going to make Ruby a great language for doing concurrent programming on the Mac," said Ernest Prabhakar, open source product manager at Apple.

Incremental releases of MacRuby have been occurring since March 2008. MacRuby is compiled by default and uses the LLVM (Low Level Virtual Machine)  project for just-in-time and ahead-of-time compilation.