I'm sorry, but in the world of awesomely-licensed Qt and other cross-platform toolkits, why would you go out of your way to build a native app on Mac libraries and only release it for a single platform?
I can understand that OS X probably has the biggest share of GitHub visitors, but git is fully open source, GitHub seem to very much like open source, and in the spirit of that I'd expect a native app that works on as many platforms as possible.
a native app that works on as many platforms as possible
The definition of native app has changed. It's no longer a synonym for compiled binary; or using native widget. It is not as simple as coding your UI in a cross-platform toolkit. In these days, a native app means something that feels like the built-in apps: it's beyond skinning and appearance and is more about how the app as a whole interacts with the user to get the job done. As the platforms diverge, it's now really hard - if not impossible - to make a cross-platform native app. Among Performance, Cost, Time, Scope, you can only pick three. GitHub sacrifices the scope.
Reminds me of when Intuit was building out Quicken -- most of their versions were built using cross platform tools, but inside the code it became a big mess and most recently they decided to scrap the whole thing and re-write the mac client in native objective-c instead of c++
Sure you can build cross-platform stuff using Java or QT, but has anyone actually liked the stuff that came out from that?
Syntevo products (SmartSVN, SmartGit, SmartSynchronize) are actually bearable. I started using SmartSVN back when I used to use three platforms for desktop (Win, Linux, Mac) interchangeably and continued using it for subversion after moving to Mac.
Won't see myself using SmartGit though (we are moving to git). Will stick to command line with occasional launch of GitX or other native client.
I can understand that OS X probably has the biggest share of GitHub visitors, but git is fully open source, GitHub seem to very much like open source, and in the spirit of that I'd expect a native app that works on as many platforms as possible.