In spite of what you might still read on http://www.mono-project.com/, mono source moved to github.com/mono/mono. To build and compile on the mac however the simplest instructions are still the "One Stop Shop Build Script" at the bottom of http://www.mono-project.com/Compiling_Mono_on_OSX. They worked for me first time although I hit a couple of issues:
- Having a space in the path to where I built it broke the build script
- Fetching the mono repo from git failed several times. This may - or may not - be related to the OS X 10.9 Mavericks / Versions issue noted at http://www.git-tower.com/blog/make-git-rebase-safe-on-osx/ but I've had no further problems since following their instruction to
git config --global core.trustctime false