The MacMAME project is no longer active because of Brad Oliver's work obligations as a program writer for a respectable software company and he has also cited Apple's deprecation of Carbon. (...and it came out a diamond!)

MAME is still under development and on the Mac there are a few projects.

First is MAME OS X - a special Mac version that takes advantage of all Mac OS X's core technologies.

Second is SDLMAME which it looks like you have to compile yourself (lots of information at rbelmont.mameworld.info).

Third is Advance MAME and Advance MENU which runs in X-Windows and can be installed through FINK.