Looks promising! May I ask why you forked from the original (https://github.com/JamesFator/GoogleMusicMac)? Looking at the commit history it seems to be under active development.
Thanks! When I initially forked the repository, I hadn't planned on including features like the theme or the notifications, but once I realized how much I liked the product and wanted to continue to develop it, I figured I should ask the original creator for permission to keep the fork independent and he agreed. Very generous of him!
Outside of implementing the notifications this offers nothing for me that the original one, from James Fator, doesn't already do. I dislike the table display and the attempt at making the appearance be more Cocoa-esque in favor of the Google web design. You might also want to think of changing the app name and icon also as it is misleading.