TreeComp is released as a Windows application. According to the download options and information on the developer's website, the application was never planned for a Mac release, however, there is a possibility to run it in a Mac environment. You could try to install Windows via the Bootcamp feature Mac OSX offers to its users or if you have knowledge regarding computer virtualization, you could install VMWare Fusion, then add a Windows version (preferably XP or 7).
I recommend using Bootcamp because it's free and there are less steps towards the completion rather than using VMWare Fusion. You can check for the Bootcamp tutorial on the Apple Support website.