Qube is both an app store and an application development framework for the Windows, Mac, Linux, and BSD platforms. With Qube, a user can download and install applications from the App Store onto any given computer, and developers can build good looking, highly functional apps that work on any platform, without having to worry about cross-platform compatibility.
For one, there is no other cross-platform app store that allows a given application to run on Windows, Mac, Linux, and BSD operating systems. With Qube, a developer can build an app one time, in one language, and expect it to work perfectly on any platform.
Secondly, we do not like the idea of a "walled-garden" software ecosystem. Platforms like the Apple App Store and the Google Play store do just that - they wall us into a controlled environment to which only they have control. That's not to say we don't like the idea of a central "repository" for applications, but we don't like the idea of having that repository in the hands of a corporation or government whose sole motivation is profit or control.
Qube runs on the Java runtime environment, which itself being open and cross-platform, offers a foundation to create a user-friendly, developer-centric ecosystem. This, in turn, enables developers to build applications more efficiently by making use of one programming language and runtime (Java+JRE) and to distribute applications more effectively than the various proprietary app stores (one app for all platforms vs. separate compiled binaries for each platform - or even complete rewrites).