MacHg is described as 'free open source OSX GUI for the revision control system Mercurial' and is an app in the Development category. There are six alternatives to MacHg for Mac, Windows, Linux and Java. The best alternative is SmartGit. It's not free, so if you're looking for a free alternative, you could try Sourcetree or TortoiseHg. Other great apps like MacHg are EasyMercurial (Free, Open Source), Murky (Free, Open Source) and Source App (Free, Open Source).
SmartGit is a front-end for the distributed version control system Git and runs on Windows, Mac OS X and Linux. SmartGit is intended for developers who prefer a graphical user interface over a command line client, to be even more productive with Git.
TortoiseHg is an easy to use client for the Mercurial (Hg) distributed revision control system. TortoiseHg adds shell integration into Windows and Linux (Gnome/Nautilus) and includes a command line wrapper.
EasyMercurial is a simple user interface for the Mercurial distributed version control system. It's free, open source, and cross-platform. We have set out to make EasyMercurial straightforward to teach and learn.
Murky is a GUI client app for the Mercurial distributed version-control system. It lets you manage repositories and source files without using a command-line. Murky runs on Mac OS X 10.5 or later. It's written in Objective-C 2.0. It's released under a BSD license.