Graph is a native Windows application but can be run on a Mac through Wine. The link below allows you to download a package with both Graph and Wine. When downloaded OS X will extract the file Graph.app in your Download folder. You can just move it to the Applications folder and afterwards start Graph from the Launchpad.
GraphBeta-126.96.36.1992-2.app.zip (100 MB)
The package will run Graph on a Mac with Wine as a compatibility layer. This means that some minor problems and incompatibilities are to be expected. In addition this is a beta version, which means that Graph may contain some bugs and unfinished features as well.
In the future a native OS X version of Graph may be available.