The linked repository provided patches for the official Spotify app. It looks like you’re supposed to fetch the Spotify APK, unpack it with apktool, apply the patch from the version tag in the repository (which also includes binary changes to native libraries), and put the APK together.
While some parts of the patches are open, some binary changes aren’t. And the original app is closed, so I don’t think this app would be eligible for inclusion within Android. Redistributing the modified APK is probably not allowed either.
See also the XDA thread.