We have helped build a test version of the Kokua viewer for Mac.
It has been built with the Clang compiler in Xcode 6.4 and SDK 10.9, and is based on Linden Lab's 3.8.1 code base with the OpenSim additions and general improvements in the Kokua viewer.
This version also has a couple OpenSim related fixes in addition to all the bug fixes and improvements that is included in the Linden code (see the release notes for the SL viewer for details.)
It has been tested on all the major OpenSim grids both with direct login and hypergrid teleports in addition to SecondLife. You need OS X 10.8 or higher to run this version of the viewer.
This build is a major step forward for the Mac viewer since building it with Clang and not old GCC viewer that Apple discontinued support for in OS X 10.8 lays the foundation for building a 64-bit version of the viewer with the modern frameworks that Apple provides.
It can be downloaded via this blog post. Please report any issues via the Kokua ticketing system.
UPDATE: It is also possible to get the latest builds from Bitbucket while SourceForge is unavailable.