Can I back up tags / whatever that I make, and will they sync between multiple devices?
Is the app open-sourced? Will it be? Are you planning to charge for the app? For premium features?
Most importantly, why are the features you're providing going to improve my experience with GitHub?
These are all questions I'd expect the landing page to answer.
Sure, it may not have all the features that the site has but it excels at being that convenience bridge between what's on my filesystem and what's on the site.
So also, if it's not for all platforms (web?) then please, platform should be in the title.
The only thing this app appears to do is let you "tag" repositories.
Into the trash it goes...
https://windows.github.com/ https://mac.github.com/
I have shown the windows version to a few people and they grokked git a lot better than if I tried via the standard toolkit.
If you like the app, though, you might want to check out Astral (https://astralapp.com). Extremely similar functionality, but Astral runs in your browser.
I guess the main value-add I could see would be notifications when people open issues, send PRs, or fork repos of mine. Does this app display them?